Determining the electrical switch-on time using the load voltage for the combined load

Abstract

A method for detecting an electrical closing time of a coupled load is provided. During energization operation of the electrical equipment via a switching device, measured terminal voltages for each of one or more phases of the electrical equipment are obtained from a voltage measurement device, the phases of the electrical equipment being electrically or magnetically coupled to one another. Further, circuit configuration parameters associated with the electrical equipment are obtained. Based on one or more of the measured terminal voltages of the electrical equipment and a mapping table, a processing voltage is determined for one or more phases of the electrical equipment. The mapping table includes a mapping between the circuit configuration parameters and calculations performed on one or more of the measured terminal voltages. Based on the processing voltage, an electrical closing time of a pole of a switching device associated with a phase of the one or more phases is determined to monitor energization operation of the electrical equipment.

Description

[Technical field]

[0001] Technical Field The present subject matter relates generally to determining an electrical turn-on point. In particular, the present subject matter relates to determining an electrical turn-on point using a load voltage for a coupled load. [Background technology]

[0002] background Switching devices such as circuit breakers are commonly used in power systems for controlled switching of electrical equipment such as transformers, reactor banks, or capacitor banks. During operation of a power system, an electrical equipment may be switched on and off using a circuit breaker connected thereto. Switching on and switching off of an electrical equipment may be referred to as energizing and de-energizing, respectively. The energizing and de-energizing of an electrical equipment is done considering various factors such as load variations, fault detection, etc. One phase of an electrical equipment may be electrically, magnetically, or both coupled to another phase of an electrical equipment. The point in time when the circuit breaker contacts engage or close and a current signal is generated for energizing the electrical equipment may be referred to as the electrical closing point of the circuit breaker. A controlled switching device (CSD) may compare the actual electrical closing point of time with a corresponding target electrical closing point of time and, based on the comparison, optimizes the operating time of the circuit breaker for subsequent energization. This process of adaptive correction compensates for systematic changes such as operational variations due to effects such as aging, contact wear, gas pressure fluctuations, etc. that may affect the operating characteristics of the circuit breaker. Summary of the Invention [Problem to be solved by the invention]

[0003] overview An embodiment of the present invention provides a method for determining an electrical closing time of a switching device, such as a circuit breaker, for energizing an electrical device. The determination of the actual time of operation of the circuit breaker to energize the electrical device may be referred to as the electrical closing time. An apparatus is provided for determining an electrical closing time of a switching device for controlled switching and monitoring the energization operation of a combined load, and a computer-readable storage medium is provided that includes instructions for determining an electrical closing time of a switching device for controlled switching and monitoring the energization operation of the combined load. Objectives of embodiments of the present invention include accurate assessment of the actual electrical closing time of two or more phases of a combined load to facilitate optimized controlled switching and monitoring of the energization operation of the combined load. Embodiments of the present invention provide a quick and simple approach for detecting the electrical closing time based on terminal voltage measurements. [Means for solving the problem]

[0004] According to a first aspect, a method is provided for determining electrical closing time points of switching devices for monitoring energization operation of an electric device. The method includes obtaining measured terminal voltages of each of one or more phases of the electric device from a voltage measurement device during energization operation of the electric device via the switching device, the phases of the electric device being electrically or magnetically coupled to each other. Further, circuit configuration parameters associated with the electric device are obtained. Further, a processing voltage is determined for one or more phases of the electric device based on one or more of the measured terminal voltages of the electric device and a mapping table. The mapping table includes a mapping between the circuit configuration parameters and calculations performed on one or more of the measured terminal voltages to determine the processing voltage. Based on the processing voltage, an electrical closing time point of a pole of a switching device associated with a phase of the one or more phases is determined for monitoring energization operation of the electric device.

[0005] According to a second aspect, an apparatus is provided, connected to a switching device and comprising a processor, the processor being configured to obtain, from a voltage measurement device, a measured terminal voltage for each of one or more phases of the electric equipment during energization operation of the electric equipment through the switching device, the phases of the electric equipment being electrically or magnetically coupled to each other. Further, a circuit configuration parameter associated with the electric equipment is obtained. Further, a processing voltage is determined for one or more phases of the electric equipment based on one or more of the measured terminal voltages of the electric equipment and a mapping table. The mapping table includes a mapping between the circuit configuration parameter and a calculation performed on one or more of the measured terminal voltages to determine the processing voltage. Based on the processed voltage, an electrical closing time point of a pole of the switching device associated with a phase of the one or more phases is determined to monitor the energization operation of the electric equipment.

[0006] According to one embodiment, monitoring the energization of the electrical equipment includes evaluating a closing time based on a determined electrical closing time of a pole of a switching device during the energization operation, comparing the closing time to an expected closing time for a circuit configuration parameter to determine an error, and applying a correction to the closing time of the pole of the switching device based on the determined error to improve performance of the subsequent energization operation.

[0007] According to one embodiment, if the electrical equipment is inductive having a magnetic circuit, the step of determining the process voltage comprises determining a winding voltage, the winding voltage generating a magnetic flux linking each phase of the electrical equipment.

[0008] According to one embodiment, when the electrical equipment is a capacitor bank, the step of determining the process voltage comprises determining a voltage across an equivalent capacitance for each phase of the electrical equipment.

[0009] According to one embodiment, the measured terminal voltages for each phase are obtained from a voltage measurement device connected to the load side of the switching device.

[0010] According to one embodiment, the electrical closing instant of the poles of the switching device is determined as the instant corresponding to the start of the rising slope of the process voltage when the rising slope crosses a predefined per-phase threshold value to reach a first voltage peak.

[0011] According to one embodiment, the predefined per-phase thresholds correspond to one or more of noise, interference, or sub-properties of the electrical device.

[0012] According to one embodiment, the circuit configuration parameters include one or more of the following: a connection configuration of a voltage measuring device, a location of a voltage measuring device, a type of voltage measuring device, design characteristics of the electrical equipment, the number of windings and their connection configuration, the type of winding configuration in which controlled switching is performed, and a switching sequence of the electrical equipment.

[0013] According to one embodiment, the measured terminal voltages of any one of the one or more phases or any two of the one or more phases are used to determine a process voltage for detecting the electrical closing instant of a pole of a switching device associated with any other of the one or more phases based on a mapping table.

[0014] According to one embodiment, the electrical device is one of a transformer, a delta connected or ungrounded capacitor bank, a delta connected or ungrounded non-magnetically coupled reactor, or a magnetically coupled reactor.

[0015] BRIEF DESCRIPTION OF THE DRAWINGS The features, aspects, and advantages of the present subject matter will become better understood with regard to the following description and the accompanying drawings, in which: The use of the same reference numbers in different figures indicates similar or identical features and components. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 illustrates a block diagram for monitoring energized operation of an electrical device, according to one embodiment of the present subject matter. [Figure 2(a)]1 illustrates a block diagram of a first configuration for monitoring the energization operation of a transformer, according to one embodiment of the present subject matter. [Figure 2(b)] 1 illustrates line-to-ground measurement terminal voltages obtained for a first configuration, according to one embodiment of the present subject matter. [Figure 2(c)] 1 illustrates processing voltages determined for a first configuration, according to one embodiment of the present subject matter. [Figure 2(d)] 1 illustrates compensation of processed voltage signals based on predetermined per-phase thresholds for a first configuration, according to one embodiment of the present subject matter. [Figure 3(a)] FIG. 2 illustrates a block diagram of a second configuration for monitoring the energization operation of a transformer, according to an embodiment of the present subject matter. [Figure 3(b)] 13 illustrates line-to-line measured terminal voltages obtained for a second configuration, according to one embodiment of the present subject matter. [Figure 3(c)] 13 illustrates derived winding voltages determined for a second configuration, according to one embodiment of the present subject matter. [Figure 3(d)] 13 illustrates processing voltages determined for a second configuration, according to one embodiment of the present subject matter. [Figure 4(a)] 1 illustrates a block diagram of a third configuration for monitoring the energization operation of a transformer, according to an embodiment of the present subject matter. [Figure 4(b)] 13 illustrates line-to-ground measurement terminal voltages obtained for a third configuration, according to one embodiment of the present subject matter. [Figure 4(c)] 13 illustrates derived winding voltages for a third configuration, according to one embodiment of the present subject matter. [Figure 4(d)] 13 illustrates process voltages determined for a third configuration, according to one embodiment of the present subject matter. [Figure 5(a)] FIG. 13 shows a block diagram of a fourth configuration for monitoring the conduction operation of a delta-connected capacitor bank, according to an embodiment of the present subject matter. [Figure 5(b)] 13 illustrates line-to-ground measurement terminal voltages obtained for a fourth configuration, according to one embodiment of the present subject matter. [Figure 5(c)] 13 illustrates equivalent voltages per phase derived for a fourth configuration, according to one embodiment of the present subject matter. [Figure 5(d)] 13 illustrates process voltages determined for a fourth configuration, according to one embodiment of the present subject matter. [Figure 6] 1 illustrates a method for determining an electrical turn-on time of a switching device, according to one embodiment of the present subject matter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Detailed Description The subject matter relates to determining an electrical closing time of a switching device. In the following, determining an electrical closing time of a switching device for monitoring the energization operation of a coupled load is described. Hereinafter, the switching device is also referred to as a circuit breaker. The time of operation of the contacts of the circuit breaker in response to a closing command is defined as the electrical closing time of the circuit breaker. In one example, each pole of the circuit breaker may be associated with a phase of an electric device. For the purposes of illustration, the coupled load referred to herein may be an electric device. The electric device may have one or more phases that are magnetically, electrically, or both coupled. For example, an electric device having a delta connection or an ungrounded neutral connection is considered to be electrically coupled, and an electric device having a three-legged core is considered to be magnetically coupled.

[0018] In one technique, a current feedback signal is used to determine the electrical closing time of the circuit breaker. This technique is generally applicable to electrical equipment such as reactor or capacitor banks. In another technique, a load voltage signal is used to determine the electrical closing time of the circuit breaker. In the case of electrical equipment such as transformers, or in transmission line applications, the load voltage signal is used to determine the electrical closing time.

[0019] In an electric device in which one or more phases are electrically or magnetically coupled, when a first pole of a circuit breaker associated with a first phase of the electric device is closed, a load voltage appears on two or more phases associated with the electric device. This is undesirable because it becomes a challenge to determine the electrical closing time for each phase of the electric device. Therefore, it can be a challenge to distinguish the individual electrical closing times for each phase of the electric device. In the case of an electric device such as a transformer, the optimal switching time for each phase of the transformer can be determined from the transformer core residual flux pattern. In the case of a transformer, measurements of the transformer terminal voltage and mathematical integration of the winding voltage may be performed to determine the transformer core residual flux pattern. The optimal electrical closing time may be determined based on the residual flux obtained from the direct load voltage. Detecting the individual electrical closing times from the direct load voltage signal may result in erroneous detection of the closing times of the electrically and / or magnetically coupled loads.

[0020] The present subject matter provides methods and apparatus for determining electrical turn-on times for two or more phases of an electric device by determining a process voltage based on one or more of the measured terminal voltages and a mapping table. The electrical turn-on times of switching devices, such as circuit breakers, may be utilized to monitor the energization operation of the electric device. The electric device may be electrically, magnetically, or both coupled. Although the principles of the present subject matter are primarily described with respect to transformers as the electric device, the same principles are applicable to other electric devices, such as capacitor banks, reactor banks, etc., where the phases of the electric device may be coupled to each other.

[0021] In operation, in one example, during energization operation of the electric equipment through the switching device, measured terminal voltages for each phase of one or more phases of the electric equipment are obtained from a voltage measurement device, and the phases of the electric equipment are electrically or magnetically coupled to each other. Further, circuit configuration parameters associated with the electric equipment are obtained. Based on one or more of the measured terminal voltages of the electric equipment and the mapping table, a process voltage is determined for one or more phases of the electric equipment. Further, based on the process voltage, an electrical closing time point of a pole of the switching device associated with a phase of the one or more phases is determined to monitor the energization operation of the electric equipment.

[0022] Thus, the present subject matter provides for accurate determination of electrical turn-on times for rapid, optimized, controlled switching of coupled loads by distinguishing the individual electrical turn-on times for each phase of an electrical equipment from the process voltage. The present subject matter provides a fast and simple technique for reliably detecting the electrical turn-on times for individual phases of an electrical equipment in order to monitor the electrical equipment energization operation and improve the performance of subsequent energization operations.

[0023] The above and other features, aspects, and advantages of the present subject matter will be better described with reference to the following description and accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the following description to refer to the same or like parts. Several examples are described, although modifications, adaptations, and other implementations are possible.

[0024] FIG. 1 illustrates a block diagram for monitoring energized operation of an electric device, according to one embodiment of the present subject matter. The electric network 100 may be, for example, a three-phase electric network. The electric network 100 includes a power source 102 that provides power to three phases of the network 100. In one example, the power source 102 may be a generator, such as a synchronous generator, an inverter-based power source, or a busbar source. The electric device 104 may be a coupled load, i.e., an electric device in which one or more phases of the electric device are electrically or magnetically coupled to each other. In one example, the electric device 104 may be an electric and / or magnetically coupled transformer, a delta-connected capacitor bank, an ungrounded capacitor bank, a delta-connected reactor, an ungrounded non-magnetically coupled reactor, or a magnetically coupled reactor. The electric device 104 may be connected to a load side 105 of a switching device 106, such as a circuit breaker 106. Each pole of the circuit breaker 106 may be associated with a phase of the electric device 104.

[0025] It will be appreciated that electrical network 100 may include a number of additional components or devices for monitoring, sensing, and controlling various parameters that may be associated with the network but are not shown for the sake of brevity. For example, additional circuit breakers, sensors, current transformers, voltage transformers, loads connected to the transmission lines, shunt reactors, intelligent electronic devices (IEDs), protective relays, and other components may be connected to the network.

[0026] The device 108 may receive voltage measurements associated with the electrical equipment 104. In one example, the device 108 may be an IED. In another example, the device 108 may be any computing device, such as a server, desktop device, laptop, etc., that may receive measurements from an IED. In one example, the device 108 may be connected to a switching device. In another example, the device 108 may be part of a switching device. In one example, a signal may be applied directly to the switching device 106 to turn the switching device on (closed) or off (open). The switching on or off of a circuit breaker may be used for controlled switching of the electrical equipment 104.

[0027] In one example, the subject matter may be implemented by one or more modules. The modules may be implemented as instructions executable by one or more processors. For example, in an example where the device 108 executes a method for determining electrical closing time of a circuit breaker for a coupled load, the modules are executed by a processor of the device 108. If the method is partially implemented by the device 108 and partially implemented by a server, the modules (depending on the steps) are distributed between the device 108 and the server accordingly.

[0028] In one example, the device 108 may be configured to receive input measurement signals from various measurement devices connected to the electrical circuitry 100, such as current transformers, potential transformers, Rogowski coils, or other measurement sensors. In one example, the device 108 may be configured to obtain a measured terminal voltage of the electrical device 104 from a voltage measurement device (not shown). The device 108 may process the obtained voltage measurements with the aid of a processor 110. The processor 110 may be implemented as a dedicated processor, a shared processor, or multiple individual processors, some of which may be shared, some of which may be on the device 108 and others on other devices. The device 108 may comprise a memory 112 that may be communicatively connected to the processor 110. Among other functions, the processor 110 may fetch and execute computer-readable instructions stored in the memory 112. In one example, the memory 112 may store instructions that may be executed by the processor 110 to implement an electrical input instant detection module 114, alternatively referred to as an EMID module 114. In other examples, instructions for implementing the EMID module 114 may be stored in memory external to the device 108 in an external memory. The memory 112 may include any non-transitory computer-readable medium including, for example, volatile memory, such as RAM, or non-volatile memory, such as EPROM, flash memory, etc.

[0029] In one example, the method for determining an electrical closing time of the circuit breaker 106 for monitoring the energization operation of the electric equipment 104 may be executed by the processor 110 by implementing the EMID module 114. For the determination, a measured terminal voltage for each phase of the electric equipment 104 may be obtained. In one example, the measured terminal voltage for each phase may be obtained from a voltage measurement device connected to the load side 105 of the circuit breaker 106 during the energization operation of the electric equipment 104, the electric equipment 104 being energized through the circuit breaker 106. Upon obtaining the measured terminal voltage, the device 108 may obtain circuit configuration parameters associated with the electric equipment 104. In one example, the circuit configuration parameters may be obtained from a user. In another example, the circuit configuration parameters may be obtained from an external device.

[0030] The power source 102, the circuit breaker 106, the electrical equipment 104, and the measurement equipment (not shown) comprise a circuit. The circuit configuration parameters may include one or more of the following: a connection configuration of the voltage measurement equipment, a location of the voltage measurement equipment, a type of the voltage measurement equipment, design characteristics of the electrical equipment, the number of windings and their connection configuration, the type of electrical equipment on which controlled switching is performed, and a switching sequence of the electrical equipment, etc. The connection configuration of the voltage measurement equipment may refer to how the windings of the voltage measurement equipment are connected. For example, the connection configuration of the voltage measurement equipment may indicate that the voltage measurement equipment is a star-grounded or delta-connected potential transformer. The location of the voltage measurement equipment refers to the side of the electrical equipment to which the voltage measurement equipment is connected. For example, if the electrical equipment is a star-delta transformer, the location of the voltage measurement equipment may refer to the voltage measurement equipment being connected to the star side of the transformer, or the delta side of the transformer. Design characteristics of electrical equipment such as a transformer may include the core design of the transformer, how the delta connections on the windings are formed, etc. The switching sequence refers to the order in which the poles of the circuit breaker associated with the phases of the electrical equipment are closed. The characteristic of the electrical machine 104 for which controlled switching is performed may be, for example, a transformer, a capacitor bank, or a reactor bank, and the configuration of all windings of the electrical machine.

[0031] Upon obtaining the measured terminal voltages and the circuit configuration parameters, the apparatus 108 may determine a process voltage for one or more phases of the electrical equipment 104. The process voltage may be any one of the measured terminal voltages or may be obtained based on one or more measured terminal voltages.

[0032] In one example, if the electric equipment 104 is inductive having a magnetic circuit, determining the process voltage may be performed by determining a winding voltage that generates a magnetic flux that links each phase of the electric equipment 104. In yet another example, if the electric equipment 104 is a capacitor bank, determining the process voltage may be performed by determining a voltage across an equivalent capacitance for each phase of the electric equipment 104.

[0033] A mapping table may be used to determine the process voltage from the measured terminal voltages versus the obtained circuit configuration parameters. The mapping table may include a mapping between the circuit configuration parameters and calculations performed on the measured terminal voltages to determine the process voltage. In one example, the mapping table may be theoretically determined by circuit analysis. In one example, the mapping table may be stored in memory 112. In another example, the mapping table may be stored in an external memory that may be accessed by device 108. In one example, the mapping table may be preconfigured in device 108. Table 1, shown below, represents an example mapping table for an example circuit configuration in which the electrical device is a transformer. It will be understood that the mapping table may be entered for other circuit configurations as well. Furthermore, the principles may be extended to any electrical device having electrical coupling, magnetic coupling, or both electrical and magnetic coupling. For example, the principles may be extended to a delta-connected capacitor bank in which one or more phases are electrically coupled to each other, or a three-legged reactor with magnetic coupling.

[0034] Table 1 shows the mapping between transformer switching winding configurations and the calculations performed on the winding voltages to determine the process voltages. Measured terminal voltages may be obtained for each phase of the transformer. The winding voltages may be derived from the measured terminal voltages based on the connection type of the voltage measurement, the location of the voltage measurement, and the connection configuration of the windings of the electrical equipment on which the voltage measurement is made. The winding voltages remain the same for a given transformer configuration, regardless of the configuration of the voltage measurement device and regardless of the side on which the measured terminal voltages are obtained.

[0035] [Table 1]

[0036] Table 1 shows a list of transformer switching winding configurations. The transformer switching winding configurations represent the winding configurations on the energized side of the transformer. Table 1 shows some exemplary transformer switching configurations, where Yn represents a star grounded winding configuration, Y represents a star ungrounded winding configuration, D1 represents a delta winding configuration where the voltage at the energized side terminal of the transformer for each phase lags the winding voltage by 30 degrees, D11 represents a delta winding configuration where the voltage at the energized side terminal of the transformer for each phase leads the winding voltage by 30 degrees, and D5 represents a delta winding configuration where the voltage at the energized side terminal of the transformer for each phase leads the winding voltage by 30 degrees. D7 represents a delta winding configuration in which the voltage at the terminal on the transformer side for each phase leads the winding voltage by 150 degrees, D8 represents a delta winding configuration in which the voltage at the terminal on the transformer side for each phase leads the winding voltage by 150 degrees, Zn1 represents a zigzag ground winding configuration in which the voltage at the terminal on the transformer side for each phase lags the winding voltage by 30 degrees, and Zn11 represents a zigzag ground winding configuration in which the voltage at the terminal on the transformer side for each phase leads the winding voltage by 30 degrees.

[0037] Table 1 also represents a switching sequence of L1-L3-L2. In the switching sequence of L1-L3-L2, L1 may correspond to a first pole of a circuit breaker associated with a first phase of the transformer, referred to as the first switching phase L1, L3 may correspond to a third pole of a circuit breaker associated with a third phase of the transformer, referred to as the second switching phase L3, and L2 may correspond to a second pole of a circuit breaker associated with a second phase of the transformer, referred to as the third switching phase L2. Thus, the switching sequence L1-L3-L2 corresponds to energizing the phases of the electrical equipment in a 1-3-2 order by closing the poles of the circuit breakers associated with that phase.

[0038] To determine the processing voltage, the device 108 may obtain the measured terminal voltage and circuit configuration parameters. In one example, the circuit configuration parameters include details such as the energized side of the transformer and the switching sequence for energization to be followed. Based on the obtained circuit configuration parameters, the device 108 may determine the processing voltage based on a mapping table (see Table 1 for an example of this).

[0039] Based on the mapping relationship provided in Table 1, it can be seen from the first row that, in the case of a transformer energized from the star-grounded side, when the switching sequence to be followed is L1-L3-L2, the process voltages can be determined for the first switching phase L1 and the second switching phase L3 as described below.

[0040] The process voltage for the first switching phase L1 of the transformer may be determined as shown in equation (1) below.

[0041] Vp1 = (Vw1 - Vw2) / sqrt(3) (1) where Vp1 is the process voltage for the first switching phase L1 of the transformer, and Vw1 and Vw2 are the winding voltages of the first and third switching phases of the transformer, respectively. The winding voltages Vw1 and Vw2 may be calculated from the measured terminal voltages of one or more phases of the transformer based on a mapping table. In one example, the winding voltages may be based on the connection configuration of the voltage measurement device and the type of transformer winding connection from which the measured terminal voltages are obtained. In one example, the winding voltages may be the same as the measured terminal voltages. In another example, the winding voltages may be the measured terminal voltages of any one phase or combination of phases of the transformer.

[0042] Similarly, the process voltage for the second switching phase L3 of the transformer may be determined as shown in equation (2) below.

[0043] Vp3 = (Vw2 - Vw3) / sqrt(3) (2) where Vp3 is the process voltage for the second switching phase L3 of the transformer and Vw3 is the winding voltage of the second switching phase L3. In this example, when energizing the first switching phase L1 at a first time instant and the second switching phase L3 at a second time instant, the resulting magnetic flux for the third pole L2 is locked, so it may be irrelevant to determine the time of electrical closing of the third switching phase L2.

[0044] Considering another example, for details of the circuit configuration parameters, such as the transformer is energized from the star ungrounded side and the switching sequence for energization to be followed is L1-L3-L2, the second row of Table 1 can be referred to to determine the processing voltage. Table 1 shows that for a transformer energized from the star ungrounded side, with a switching sequence of L1-L3-L2, the processing voltage can be determined for the third switching phase L2 and the second switching phase L3. The processing voltage for the third switching phase L2 of the transformer can be determined as shown in the following formula (3):

[0045] Vp2 = Vw2 (3) where Vp2 is the process voltage for the third switching phase L2 of the transformer. Similarly, the process voltage for the second switching phase L3 of the transformer may be determined as shown in equation (4) below.

[0046] Vp3 = Vw3 (4) where Vp3 is the process voltage for the second switching phase L3 of the transformer and Vw3 is the winding voltage of the second switching phase L2 of the transformer.

[0047] The process voltage may further be used to determine an electrical closing time of a pole of a switching device associated with a phase of the electric equipment 104. In one example, the electrical closing time of the pole of the switching device may be determined as a time corresponding to the beginning of the rising slope when the rising slope of the process voltage crosses a predetermined per-phase threshold to reach a first voltage peak. In one example, the predetermined per-phase threshold corresponds to one or more of noise, interference, or sub-properties of the electric equipment. The sub-properties of the electric equipment may refer to design attributes of the electric equipment such as unequal flux path lengths in the case of a three-legged core design transformer or unequal flux path lengths in the case of a reactor.

[0048] The electrical closing time of the poles of the switching device may be determined to monitor the energization operation of the electric device 104. In one example, the device 108 performs the monitoring of the energization operation of the electric device 104 and includes evaluating a closing time based on the determined electrical closing time of the poles of the switching device evaluated during the energization operation. The closing time of the poles of the switching device is the time from when the switching device receives a closing command to when the circuit is detected to be electrically closed through the determined electrical closing time. The evaluated closing time may be compared to an expected closing time for the obtained circuit configuration parameters to determine an error. Based on the error, a correction may be applied to the current closing time of the poles of the switching device to determine a closing time for a subsequent operation and achieve an improvement in the switching performance of the subsequent energization operation.

[0049] Additionally, the device 108 may include an output interface 116 for communicating results obtained from the electrical input time determination module 114, for example to a server. The output interface 116 may include various computer-readable instruction-based interfaces and hardware interfaces that enable interaction with other communication, storage, and computing devices, such as network entities, web servers, databases, and external repositories, as well as peripherals. In one example, the electrical input time values, energization targets, voltage and current measurements, etc. may be viewed on a display (not shown) connected to the output interface 116 or integrated with the device 108.

[0050] Thus, the present subject matter facilitates accurate determination of electrical turn-on time points for monitoring energization operations of a coupled load. Various example scenarios in which the teachings of the present subject matter may be applied are described with reference to Figures 2(a)-5(d).

[0051] FIG. 2(a) illustrates a block diagram of a first configuration 200 for monitoring the energization operation of a transformer, according to one embodiment of the present subject matter. The first configuration 200 illustrates a star-grounded-delta (YNd11) three-leg core transformer 202, alternatively referred to as transformer 202. The YN designation of the YNd11 transformer 202 indicates that the transformer 202 is star-grounded on the first side 202A, and the d designation indicates that the transformer 202 is connected in a delta connection on the second side 202B. The YNd11 connection indicates that the terminal voltages of the phases of the transformer measured from the second side 202B lead the terminal voltages measured from the first side 202A by 30 degrees. Additionally, no load is connected to the second side 202B of the transformer 202. The three-legged core of the transformer 202 provides the magnetic coupling and the delta connection provides the electrical coupling of the transformer 202, thus the transformer 202 is magnetically and electrically coupled.

[0052] A three-phase alternating current (AC) power source 204 provides power to the transformer 202. In one example, the power source 204 may provide power to three phases of the transformer 202. A circuit breaker 206 is connected between the power source 204 and the transformer 202. Each pole of the circuit breaker 206 is associated with a phase of the transformer 202. A first portion 208 represents a power source side of the circuit breaker 206, and a second portion 210 represents a load side 210 of the circuit breaker 206. The transformer 202 is connected to the load side 210 of the circuit breaker 206.

[0053] In a first configuration 200, the transformer 202 is energized from a first side 202A, which is the star ground side of the transformer 202. The voltage measurement devices 212 may measure the terminal voltages of each phase of the transformer 202. In this configuration 200, the voltage measurement devices 212 are connected to the same side of energization of the transformer 202, i.e., the star ground side of the transformer 202. However, in other exemplary configurations, the voltage measurement devices may be located on any side of the transformer 202.

[0054] The device 214 of the first configuration 200 may obtain a measured reference signal from the source side of the circuit breaker 206. In one example, the measured reference signal may be any one or more of the three phases. The reference signal may be either a line-to-ground voltage measurement or a line-to-line voltage measurement. The reference signal may be obtained by the device 214 to generate a closing or opening command to close or open the circuit breaker 206, respectively. Additionally, the device 214 may obtain a measured terminal voltage of the transformer 202 measured from the load side 210 of the circuit breaker 206. The measured terminal voltage obtained by the device 214 may be used to determine an electrical closing time of a pole of the circuit breaker 206 associated with a phase of one or more phases of the transformer 202, which may alternatively be referred to as an actual operating time of the circuit breaker 206. The electrical closing time of the circuit breaker 206 may be determined to monitor the energization operation of the transformer 202.

[0055] Upon receiving the measured terminal voltages of each phase from the voltage measurement device 212, the device 214 may obtain circuit configuration parameters. In one example, the circuit configuration parameters may be provided by a user. In another example, the circuit configuration parameters may be obtained from another device. The circuit configuration parameters may include one or more of the following: a connection configuration of the voltage measurement device, a location of the voltage measurement device, a type of voltage measurement device, a design characteristic of the electrical equipment, a number of windings and their connection configuration, a type of winding configuration in which controlled switching is performed, and a switching sequence of the electrical equipment, etc. Upon obtaining the measured terminal voltages and the circuit configuration parameters, the device 214 may determine a process voltage.

[0056] The device 214 may determine a process voltage for one or more phases of the transformer 202 based on one or more of the measured terminal voltages of the transformer 202 and a mapping table. The mapping table may include a mapping between circuit configuration parameters and calculations performed on one or more of the measured terminal voltages. In the first configuration 200, the measured terminal voltages are obtained from the star-ground side of the transformer 202, which is the same side as the side on which the transformer 202 is energized. In the first configuration 200, the measured terminal voltages, measured for each phase of the transformer, are line-to-ground voltages corresponding to the winding voltages of the transformer 202. In order to reduce the effect of zero sequence currents, the switching sequence considered for energizing the transformer 202 is L1-L3-L2. For the switching sequence L1-L3-L2, the poles associated with the first phase of the transformer 202, also called the first switching phase L1, are closed first. The poles associated with the third phase, also called the second switching phase L3, are closed after the first poles, followed by the poles associated with the second phase, also called the third switching phase L2. The first switching phase L1 is energized at the line-to-ground voltage peak of the power supply voltage signal, considering negligible residual magnetic flux. The second switching phase L3 is energized a quarter cycle after the first switching phase L1 is energized, and the third switching phase L2 is energized a predefined time after the second switching phase L3 is energized. In one example, the device 214 corresponds to the device 108.

[0057] FIG. 2(b) illustrates the line-to-ground measurement terminal voltages obtained for the first configuration according to one embodiment of the present subject matter. Signal 220 illustrates the line-to-ground measurement terminal voltage of the first switching phase L1. Signal 230 illustrates the line-to-ground measurement terminal voltage of the second switching phase L3, and signal 240 illustrates the line-to-ground measurement terminal voltage of the third switching phase L2. From FIG. 2(b), it can be observed that upon energizing the first switching phase L1 at time instant t1, i.e., closing the first pole of the circuit breaker 206 associated with the first phase of the transformer 202 at t1, a load voltage signal also appears on the other two phases. The load voltage signal appears on all three phases of the transformer 202 due to the electrical and magnetic coupling of the transformer. Due to this effect, it can be a challenge to determine the electrical turn-on time for the second switching phase L3 and the third switching phase L2.

[0058] The measured terminal voltages obtained from the transformer 202 are further processed to determine the electrical closing time of the second switching phase L3 and the third switching phase L2 individually. In one example, when energizing the first switching phase L1 at time t1 and the second switching phase L3 at time t2, the resulting magnetic flux to the third pole L2 is locked, so determining the electrical closing time of the third switching phase L2 may be irrelevant. Therefore, the operation time of the third switching phase L2 may not affect the switching performance of the switching device, and monitoring the electrical closing time of the last switching phase in this configuration is not of primary concern. Therefore, the electrical closing of the second pole or the third switching phase L2 may not be determined in this configuration. The processed voltages may be determined to determine the electrical closing time of the circuit breaker poles associated with the phases of the transformer 202.

[0059] In one example, the process voltages of the first switching phase L1 and the second switching phase L3 may be derived based on the measured terminal voltages and a mapping table. As described above, the mapping table includes a mapping between circuit configuration parameters and calculations performed on the measured terminal voltages. Based on the mapping table, for the first configuration 200, the process voltages may be determined from equation (5) as shown below:

[0060]

number

[0061] where Vp1 and Vp3 are process voltages determined for the first switching phase L1 and the second switching phase L3, respectively.

[0062] Vm1, Vm2, and Vm3 are the measured terminal voltages of the first, third, and second switching phases, respectively, measured from the star-grounded side of the transformer 202. In one example, the process voltage may be determined only for the second switching phase L3. However, to maintain uniformity, the voltage calculation may be applied to both the first and second switching phases L1 and L3.

[0063] FIG. 2(c) illustrates a process voltage determined for the first configuration 200 according to an embodiment of the present subject matter. Signal 250 illustrates the process voltage for the first switching phase L1 energized at time instant t1. Signal 260 illustrates the process voltage for the second switching phase L3 energized at time instant t2. From FIG. 2(c), it can be observed that upon energizing the first switching phase L1 at time instant t1, a small magnitude process voltage appears on the second switching phase L3 at time instant t1. The energization of the first switching phase L1 is marked as L1 closing, and the energization of the second switching phase L3 is marked as L3 closing. The small magnitude process voltage appearing on the second switching phase L3 after energizing the first switching phase L1 at time instant t1 may be due to noise due to electrical / magnetic coupling, interference, or external system disturbance. This voltage signal may be offset by providing a predetermined threshold as shown in FIG. 2(d) for the first configuration 200. The predetermined threshold may alternatively be referred to as a predetermined per-phase threshold, since each phase may have a specific predetermined threshold. The predetermined per-phase threshold 270 (for the second switching phase L3) as shown in FIG. 2(d) may correspond to one or more of noise, interference, or sub-properties of the transformer 202. The sub-properties of the transformer 202 may correspond to unequal magnetic flux path lengths, such as in a three-legged design transformer 202. The compensation avoids erroneous detection of the electrical closing time by providing an appropriate predetermined per-phase threshold 270. The electrical closing time of the pole of the circuit breaker is determined to be a time corresponding to the beginning of the rising slope when the rising slope of the processing voltage crosses the predetermined per-phase threshold 270 to reach the first voltage peak 280. Thus, the device 214 may determine the electrical closing time of the pole of the circuit breaker 206 associated with a phase of one or more phases of the transformer 202 based on the processing voltage for monitoring the energization operation of the transformer.

[0064] FIG. 3(a) illustrates a block diagram of a second configuration 300 for monitoring the energization operation of a transformer, according to an embodiment of the present subject matter. The second configuration 300 illustrates a star-grounded-delta (YNd11) three-legged core transformer 302, alternatively referred to as transformer 302. The YN symbol of the YNd11 transformer 302 indicates that the transformer 302 is star-grounded on the first side 302A, and the d symbol indicates that the transformer 302 is connected in a delta connection on the second side 302B. The YNd11 connection indicates that the terminal voltage measured from the second side 302B of the transformer leads the terminal voltage measured from the first side 302A of the transformer by 30 degrees. The three-legged core of the transformer 302 provides the magnetic coupling, and the delta connection provides the electrical coupling of the transformer 302, such that the transformer 302 is magnetically and electrically coupled.

[0065] A three-phase alternating current (AC) power source 304 provides power to the transformer 302. In one example, the power source 304 may provide power to three phases of the transformer 302. A circuit breaker 306 is connected between the power source 304 and the transformer 302. Each pole of the circuit breaker 306 is associated with a phase of the transformer 302. A first portion 308 represents the power source side of the circuit breaker 306 and a second portion 310 represents the load side of the circuit breaker 306. The transformer 302 is connected to the load side 310 of the circuit breaker 306.

[0066] In the second configuration 300, the transformer 302 is energized from a first side 302A, which is the star ground side of the transformer 302. A voltage measurement device 312 may measure the terminal voltages of each phase of the transformer 302. In the configuration 300, the voltage measurement device 312 is connected to the second side 302B of the transformer, i.e., the delta connected side of the transformer 302.

[0067] The device 314 of the second configuration 300 may obtain a measured reference signal from the source side of the circuit breaker 306. In one example, the measured reference signal may be any one or more of the three phases. The reference signal may be either a line-to-ground voltage measurement or a line-to-line voltage measurement. The reference signal may be obtained by the device 314 to generate a closing or opening command to close or open the circuit breaker 306, respectively. Additionally, the device 314 may obtain a measured terminal voltage of the transformer 302 measured from the load side 310 of the circuit breaker 306. In this example, the measured terminal voltage is obtained from a delta winding of the transformer 302. The measured terminal voltage obtained by the device 314 may be used to determine an electrical closing time of a pole of the circuit breaker 306 associated with a phase of one or more phases of the transformer 302, which may alternatively be referred to as an actual operating time of the circuit breaker 306. The electrical closing time of the circuit breaker 306 may be determined to monitor the energization operation of the transformer 302.

[0068] Upon receiving the measured terminal voltage from the voltage measurement device 312, the device 314 may obtain circuit configuration parameters. In one example, the circuit configuration parameters may be provided by a user. In another example, the circuit configuration parameters may be obtained from another device. The circuit configuration parameters may include one or more of the following: a connection configuration of the voltage measurement device, a location of the voltage measurement device, a type of the voltage measurement device, a design characteristic of the electrical device, a number of windings and their connection configuration, a type of winding configuration in which controlled switching is performed, and a switching sequence of the electrical device, etc. Upon obtaining the measured terminal voltage and the circuit configuration parameters, the device 314 may determine a process voltage.

[0069] The device 314 may determine a process voltage for one or more phases of the transformer 302 based on one or more of the measured terminal voltages of the transformer 302 and a mapping table. The mapping table may include a mapping between circuit configuration parameters and calculations performed on one or more of the measured terminal voltages. In the second configuration 300, the measured terminal voltages are obtained from the delta winding side of the transformer 302. The measured terminal voltages measured for each phase of the transformer are line voltages that may not correspond to the winding voltages of the transformer 302, and the winding voltages may be derived from the measured terminal voltages. In order to reduce the effect of zero sequence currents, the switching sequence considered for energizing the transformer 302 is L1-L3-L2. For the switching sequence L1-L3-L2, the poles associated with the first phase of the transformer 302, also referred to as the first switching phase L1, are closed first. The poles associated with the third phase, also called the second switching phase L3, are closed after the first poles, followed by the poles associated with the second phase, also called the third switching phase L2. The first switching phase L1 is energized at the line-to-ground voltage peak, the power supply voltage signal, with negligible residual magnetic flux. The second switching phase L3 is energized a quarter cycle after the first switching phase L1 is energized, and the third switching phase L2 is energized a predefined time after the second switching phase L3 is energized, with negligible residual magnetic flux. In one example, the device 314 corresponds to the device 108.

[0070] FIG. 3(b) illustrates the line-to-line measured terminal voltages obtained for the second configuration 300, according to an embodiment of the present subject matter. Signal 320 illustrates the line-to-line measured terminal voltage of the first switching phase L1. Signal 330 illustrates the line-to-line measured terminal voltage of the second switching phase L3, and signal 340 illustrates the line-to-line measured terminal voltage of the third switching phase L2. From FIG. 3(b), it can be observed that upon energizing the first switching phase L1 at time instant t1, i.e., closing the first pole of the circuit breaker 306 associated with the first phase of the transformer 302 at t1, a load voltage signal also appears on the other two phases. The load voltage signal appears on all three phases of the transformer 302 due to the electrical and magnetic coupling of the transformer. Due to this effect, it may be a challenge to determine the electrical turn-on time point for the second switching phase L3 and the third switching phase L2 directly from the measured terminal voltages. To determine the electrical closing time of the poles of the circuit breakers associated with the phases of the transformer 302, the process voltage may be determined.

[0071] In one example, the process voltages of the first switching phase L1 and the second switching phase L3 may be derived based on the measured terminal voltages and a mapping table. As described above, the mapping includes a mapping between the circuit configuration parameters and calculations performed on the measured terminal voltages. For the second configuration 300, the process voltages may be determined from the winding voltages. The winding voltages may be derived based on equation (6), which is derived from the mapping table shown below.

[0072]

number

[0073] where Vw1, Vw3, and Vw2 are the derived winding voltages for the first switching phase L1, the second switching phase L3, and the third switching phase L2, respectively.

[0074] Vm1, Vm3, and Vm2 are the measured terminal voltages of the first switching phase L1, the second switching phase L3, and the third switching phase L2, respectively, measured from the delta winding side of the transformer 302.

[0075] In one example, processing voltages Vp1 and Vp3 for detecting the electrical on instants of the first switching phase L1 and the second switching phase L3 can be determined from the winding voltages Vw1, Vw2, and Vw3, respectively, as shown in the following equation (7):

[0076]

number

[0077] where Vp1 and Vp3 are process voltages determined for the first switching phase L1 and the second switching phase L3, respectively.

[0078] In another example, the process voltages Vp1 and Vp3 may be determined directly from the measured voltages Vm1, Vm2, and Vm3, as shown in equation (8) below.

[0079]

number

[0080] where Vp1 and Vp3 are process voltages determined for the first switching phase L1 and the second switching phase L3, respectively, and Vm1, Vm3, and Vm2 are measured terminal voltages of the first switching phase L1, the second switching phase L3, and the third switching phase L2, respectively, measured from the delta winding side of the transformer 302.

[0081] In one example, a first method of determining the process voltage directly from the measured terminal voltage may be performed, or a second method of determining the process voltage from the winding voltage may be performed. In one example, a user may select either the first method of determining the process voltage or the second method of determining the process voltage and may provide this input to device 314.

[0082] FIG. 3(c) illustrates the derived winding voltages determined for the second configuration 300, according to one embodiment of the present subject matter. Signal 350 illustrates the derived winding voltage for the first switching phase L1 energized at time instant t1. Signal 360 illustrates the derived winding voltage for the second switching phase L3 energized at time instant t2. Signal 370 illustrates the derived winding voltage for the third switching phase L2. The process voltages for the first switching phase L1 and the second switching phase L3 are derived from the derived winding voltages as shown in FIG. 3(c). The process voltages determined for the second configuration 300 are illustrated in FIG. 3(d). Signal 380 illustrates the process voltage for the first switching phase L1 energized at time instant t1. Signal 390 illustrates the process voltage for the second switching phase L3 energized at time instant t2. It can be observed that, during energization of the first switching phase L1, a small magnitude of the process voltage appears on the second switching phase L3 between time instants t1 and t2. The energization of the first switching phase L1 is marked as L1 closing, and the energization of the second switching phase L3 is marked as L3 closing, respectively. The small magnitude of the process voltage appearing on the second switching phase L3 after energizing the first switching phase L1 may be due to noise due to electrical / magnetic coupling, interference, or external system disturbance. This voltage signal may be countered by providing a predetermined per-phase threshold (not shown). Thus, the device 314 may determine an electrical closing time of the pole of the circuit breaker 306 associated with a phase of one or more phases of the transformer 302 based on the process voltage for monitoring the energization operation of the transformer. The electrical closing time of the pole of the circuit breaker device is determined as the time corresponding to the beginning of the rising slope when the rising slope of the process voltage crosses the predetermined per-phase threshold. In one example, the predetermined per-phase thresholds may correspond to one or more of noise, interference, or sub-properties of the transformer 302. The sub-properties of the transformer 302 may correspond to unequal flux path lengths, such as in a three-legged design transformer 302. This compensation avoids false detection of electrical turn-on by providing appropriate predetermined per-phase thresholds.

[0083] FIG. 4(a) illustrates a block diagram of a third configuration 400 for monitoring the energization operation of a transformer, according to an embodiment of the present subject matter. The third configuration 400 illustrates a star-grounded-delta (YNd11) three-legged core transformer 402, alternatively referred to as transformer 402. The d symbol indicates that the transformer 402 is connected in a delta connection on the first side 402A. The YN symbol of the YNd11 transformer 402 indicates that the transformer 402 is star-grounded on the second side 402B. The Yd11 connection indicates that the terminal voltage of a phase of the transformer 402 measured from the first side 402A leads the terminal voltage of that phase measured from the second side 402B by 30 degrees. The three-legged core of the transformer 402 provides the magnetic coupling, and the delta connection provides the electrical coupling of the transformer 402, such that the transformer 402 is magnetically and electrically coupled.

[0084] A three-phase alternating current (AC) power source 404 provides power to the transformer 402. In one example, the power source 404 may provide power to three phases of the transformer 402. A circuit breaker 406 is connected between the power source 404 and the transformer 402. Each pole of the circuit breaker 406 is associated with a phase of the transformer 402. A first portion 408 represents a power source side of the circuit breaker 406 and a second portion 410 represents a load side 410 of the circuit breaker 406. The transformer 402 is connected to the load side 410 of the circuit breaker 406.

[0085] In the third configuration 400, the transformer 402 is energized from a first side 402A, which is the delta (d) side of the transformer 402. The voltage measurement devices 412 may measure the terminal voltages of each phase of the transformer 402. In the third configuration 400, the voltage measurement devices 412 are connected to the same energized side of the transformer 402, i.e., the delta (d) side of the transformer 402.

[0086] The device 414 of the third configuration 400 may obtain a measured reference signal from the source side of the circuit breaker 406. In one example, the measured reference signal may be any one or more of the three phases. The reference signal may be either a line-to-ground voltage measurement or a line-to-line voltage measurement. The reference signal may be obtained by the device 414 to generate a closing or opening command to close or open the circuit breaker 406, respectively. Additionally, the device 414 may obtain a measured terminal voltage of the transformer 402 measured from the load side 410 of the circuit breaker 406. In this example, the measured terminal voltage is obtained from a delta winding of the transformer 402. The measured terminal voltage obtained by the device 414 may be used to determine an electrical closing time of a pole of the circuit breaker 406 associated with a phase of one or more phases of the transformer 402, which may alternatively be referred to as an actual operating time of the circuit breaker 406. The electrical closing time of the circuit breaker 406 may be determined to monitor the energization operation of the transformer 402.

[0087] Upon receiving the measured terminal voltages of each phase from the voltage measurement device 412, the device 414 may obtain circuit configuration parameters. In one example, the circuit configuration parameters may be provided by a user. In another example, the circuit configuration parameters may be obtained from another device. The circuit configuration parameters may include one or more of the following: a connection configuration of the voltage measurement device, a location of the voltage measurement device, a type of the voltage measurement device, a design characteristic of the electrical equipment, a number of windings and their connection configuration, a type of winding configuration in which controlled switching is performed, and a switching sequence of the electrical equipment, etc. Upon obtaining the measured terminal voltages and the circuit configuration parameters, the device 414 may determine a process voltage.

[0088] The device 414 may determine a process voltage for one or more phases of the transformer 402 based on one or more of the measured terminal voltages of the transformer 402 and a mapping table. The mapping table may include a mapping between circuit configuration parameters and calculations performed on the measured terminal voltages. In the third configuration 400, the measured terminal voltages are obtained from the delta winding side of the transformer 402. In this exemplary configuration 400, the measured terminal voltages, measured for each phase of the transformer, are the line-to-ground voltages of the transformer 402. The switching sequence considered for energizing the transformer 402 is a non-simultaneous energization strategy L1-L2-L3. In the switching sequence L1-L2-L3, the poles associated with a first phase of the transformer 402, alternatively referred to as the first switching phase L1, are closed simultaneously with the poles associated with a second phase, alternatively referred to as the second switching phase L2, followed by the poles associated with a third phase, alternatively referred to as the third switching phase L3. The first switching phase L1 and the second switching phase L2 are energized at the line voltage peak of the measured terminal voltage signal, considering negligible residual magnetic flux. The third switching phase (L3) is energized a quarter period (90 degrees) after the first and second switching phases L1, L2 are energized simultaneously. However, the first switching phase L1 is energized for a predefined duration before the second switching phase L2 to maintain the aforementioned switching sequence of L1-L2-L3. In one example, the device 414 corresponds to the device 108.

[0089] FIG. 4(b) illustrates the line-to-ground measurement terminal voltages obtained for the third configuration 400, according to an embodiment of the present subject matter. Signal 420 illustrates the line-to-ground measurement terminal voltage of the first switching phase L1. Signal 430 illustrates the line-to-ground measurement terminal voltage of the second switching phase L2, and signal 440 illustrates the line-to-ground measurement terminal voltage of the third switching phase L3. As illustrated in FIG. 4(b), direct voltage measurements cannot be used to detect the electrical closing time of the second switching phase L2 and the third switching phase L3. From the figure, it can be observed that when the first switching phase L1 is energized at time instant t1, i.e., when the first pole of the circuit breaker 406 associated with the first phase of the transformer 402 is closed, the load voltage signal also appears in the other two phases. As can be seen, when the first switching phase L1 is energized, due to the delta connection, voltage appears in all three phases. However, no current flows until the second switching phase L2 is energized. This is because there is no return path to facilitate the flow of current. Therefore, detecting the electrical on time for the first switching phase L1 is not a primary concern. Due to this effect, determining the electrical on time for the second switching phase L2 and the third switching phase L3 can be a challenge. To determine the electrical on time for the second switching phase L2 and the third switching phase L3 individually, the process voltage can be determined.

[0090] In one example, the process voltages of the second switching phase L2 and the third switching phase L3 may be derived based on one or more of the measured terminal voltages and a mapping table. As described above, the mapping includes a mapping between the circuit configuration parameters and a calculation performed on one or more of the measured terminal voltages. For the third configuration 400, the process voltages may be determined from the winding voltages. The winding voltages of the third configuration 400 may be derived based on Equation (10) based on the mapping table shown below.

[0091]

number

[0092] where Vw1, Vw2, and Vw3 are the winding voltages determined for the first switching phase L1, the second switching phase L2, and the third switching phase L3, respectively.

[0093] Vm1, Vm2, and Vm3 are the measured terminal voltages of the first switching phase L1, the second switching phase L2, and the third switching phase L3, respectively, measured from the delta winding side of the transformer 402. The derived winding voltages Vw1, Vw2, and Vw3 for the third configuration 400 are represented in FIG. 4(c) by signals 460, 480, and 470, respectively.

[0094] In one example, processing voltages Vp2 and Vp3 for detecting the electrical input instants for the second switching phase L2 and the third switching phase L3 can be determined based on the winding voltages Vw1, Vw2, and Vw3, respectively, as shown in the following equation (11):

[0095]

number

[0096] where Vp2 and Vp3 are process voltages determined for the second switching phase L2 and the third switching phase L3, respectively.

[0097] FIG. 4(d) illustrates a process voltage determined for the third configuration 400 according to an embodiment of the present subject matter. Signal 490 illustrates a process voltage for the second switching phase L2 energized at time instant t2. Signal 410 illustrates a process voltage for the third switching phase L3 energized at time instant t3. FIG. 4(d) illustrates a process voltage for the third switching phase L3, and as described above, a small magnitude voltage appears when only the second switching phase L2 is closed. Therefore, the device 414 may determine an electrical closing time of a pole of the circuit breaker 406 associated with a phase of one or more phases of the transformer 402 based on the process voltage for monitoring the energization operation of the transformer. The electrical closing time of the pole of the circuit breaker device is determined at a time corresponding to the beginning of the rising slope when the rising slope of the process voltage crosses a predetermined per-phase threshold (not shown). In one example, the predetermined per-phase threshold may correspond to one or more of noise, interference, or sub-properties of the transformer 402. Sub-properties of the transformer 402 may correspond to unequal flux path lengths, such as in a three-legged design transformer 402. By providing appropriate pre-defined per-phase thresholds, false detection of electrical make-on instant is avoided by compensating for the small magnitude of voltage when only the second switching phase is energized.

[0098] 5(a) illustrates a block diagram of a fourth configuration 500 for monitoring the energization operation of a delta-connected capacitor bank, according to one embodiment of the present subject matter. The fourth configuration 500 illustrates a delta-connected capacitor bank 502, alternatively referred to as capacitor bank 502. The capacitor bank 502 is designed to be a three-phase delta-connected capacitor bank. The delta connection of the capacitor bank 502 provides an electrical coupling of the capacitor bank.

[0099] A three-phase alternating current (AC) power source 504 provides power to the capacitor bank 502. In one example, the power source 504 may provide power to three phases of the capacitor bank 502. A circuit breaker 506 is connected between the power source 504 and the capacitor bank 502. Each pole of the circuit breaker is associated with a phase of the capacitor bank 502. A first portion 508 represents a power source side of the circuit breaker 506 and a second portion 510 represents a load side 510 of the circuit breaker 506. The capacitor bank 502 is connected to the load side 510 of the circuit breaker 506.

[0100] In the fourth configuration 500, a voltage measurement device 512 may measure the terminal voltage of each phase of the capacitor bank 502. In this fourth configuration 500, the voltage measurement device 512 is connected to the load side of the circuit breaker 506.

[0101] The device 514 of the fourth configuration 500 may obtain a measured reference signal from the source side of the circuit breaker 506. In one example, the measured reference signal may be any one or more of the three phases. The reference signal may be either a line-to-ground voltage measurement or a line-to-line voltage measurement. The reference signal may be obtained by the device 514 to generate a closing or opening command to close or open the circuit breaker 506, respectively. Additionally, the device 514 may obtain a measured terminal voltage of the capacitor bank 502 measured from the load side 510 of the circuit breaker 506. The measured terminal voltage obtained by the device 514 may be used to determine an electrical closing time of a pole of the circuit breaker 506 associated with a phase of the one or more phases of the capacitor bank 502, which is alternatively referred to as an actual operating time of the circuit breaker 506. The electrical closing time of the circuit breaker 506 may be determined to monitor the energization operation of the delta-connected capacitor bank 502.

[0102] Upon receiving the measured terminal voltage from the voltage measurement device 512, the device 514 may obtain circuit configuration parameters. In one example, the circuit configuration parameters may be provided by a user. In another example, the circuit configuration parameters may be obtained from another device. The circuit configuration parameters may include one or more of the following: a connection configuration of the voltage measurement device, a location of the voltage measurement device, a type of the voltage measurement device, a design characteristic of the electrical device, a number of windings and their connection configuration, a type of winding configuration in which controlled switching is performed, and a switching sequence of the electrical device, etc. Upon obtaining the measured terminal voltage and the circuit configuration parameters, the device 514 may determine a process voltage.

[0103] The device 514 may determine a process voltage for one or more phases of the capacitor bank 502 based on one or more of the measured terminal voltages of the capacitor bank 502 and a mapping table. The mapping table may include a mapping between circuit configuration parameters and calculations performed on one or more of the measured terminal voltages. In the fourth configuration 500, the measured terminal voltages measured for each phase of the capacitor bank 502 are the line-to-ground voltages of the capacitor bank 502. The switching sequence considered for energizing the fully discharged capacitor bank 502 is the non-simultaneous switching sequence L1-L2-L3. In the switching sequence L1-L2-L3, the poles associated with a first phase of the capacitor bank 502, alternatively referred to as the first switching phase L1, are closed simultaneously with the poles associated with a second phase, alternatively referred to as the second switching phase L2, followed by the poles associated with a third phase, alternatively referred to as the third switching phase L3. The first switching phase L1 and the second switching phase L2 are energized at the line voltage zero of the measured terminal voltage signal in consideration of the capacitor bank being discharged. The third switching phase (L3) is energized a quarter period (90 degrees) after the first and second switching phases L1, L2 are energized simultaneously. However, the first switching phase L1 is energized for a predefined duration before the second switching phase L2 to maintain the aforementioned switching sequence of L1-L2-L3. In one example, the device 514 corresponds to the device 108.

[0104] FIG. 5(b) illustrates the line-to-ground measurement terminal voltages obtained for the fourth exemplary configuration 500, according to an embodiment of the present subject matter. Signal 520 illustrates the line-to-ground measurement terminal voltage of the first switching phase L1. Signal 530 illustrates the line-to-ground measurement terminal voltage of the second switching phase L2, and signal 540 illustrates the line-to-ground measurement terminal voltage of the third switching phase L3. As illustrated in FIG. 5(b), direct voltage measurements cannot be used to detect the electrical closing time of the second switching phase L2 and the third switching phase L3. From the figure, it can be observed that when the first switching phase L1 is energized at time instant t1, i.e., when the first pole of the circuit breaker 506 associated with the first phase of the capacitor bank 502 is closed at t1, the load voltage also appears on the other two phases. As can be seen, when the first switching phase L1 is energized, due to the delta connection, the voltage appears on all three phases. However, no current flows until the second switching phase L2 is energized. This is because there is no return path to facilitate current flow. Therefore, detecting the electrical closing time for the first switching phase L1 is not a primary concern. Due to this effect, determining the electrical closing times for the second switching phase L2 and the third switching phase L3 can be a challenge. To determine the electrical closing times of the circuit breaker poles associated with the phases of the capacitor bank 502, the process voltage can be determined.

[0105] In one example, the process voltages of the second switching phase L2 and the third switching phase L3 may be derived based on the measured terminal voltages and a mapping table. As described above, the mapping table includes a mapping between the circuit configuration parameters and a calculation performed on the measured terminal voltage table. For the fourth configuration 500, the process voltages may be determined from the voltages across the equivalent capacitances for each phase, also referred to as equivalent voltages per phase. The voltages across the equivalent capacitances for each phase of the capacitor bank 502 may be determined based on equation (12) based on the mapping table shown below.

[0106]

number

[0107] where Vm1, Vm2, and Vm3 are the measured terminal voltages of the first switching phase L1, the second switching phase L2, and the third switching phase L3, respectively, measured from the capacitor bank 502; Ve1, Ve2, and Ve3 are the equivalent voltages per phase for the first switching phase L1, the second switching phase L2, and the third switching phase L3, respectively.

[0108] Further, based on the derived equivalent voltages per phase, the process voltage of the fourth configuration 500 can be derived based on equation (13) based on the mapping table shown below.

[0109]

number

[0110] where Vp2 and Vp3 are process voltages determined for the second switching phase L2 and the third switching phase L3, respectively.

[0111] FIG. 5(c) illustrates the equivalent voltages per phase derived for the fourth configuration, according to one embodiment of the present subject matter. Signal 550 illustrates the equivalent voltage for the first switching phase L1. Signal 560 illustrates the equivalent voltage for the second switching phase L2, and signal 570 illustrates the equivalent voltage for the third switching phase L3. The process voltages as illustrated in FIG. 5(d) are derived from the equivalent voltages per phase as illustrated in FIG. 5(c).

[0112] FIG. 5(d) illustrates a process voltage determined for the fourth configuration 500 according to an embodiment of the present subject matter. Signal 580 illustrates the process voltage for the second switching phase L2 energized at time instant t2. Signal 590 illustrates the process voltage for the third switching phase L3 energized at time instant t3. Thus, the device 514 may determine an electrical closing time of a pole of the circuit breaker 506 associated with a phase of one or more phases of the capacitor bank 502 based on the process voltage for monitoring the energization operation of the capacitor bank 502. The electrical closing time of the pole of the circuit breaker device is determined at a time corresponding to the beginning of the rising slope when the rising slope of the process voltage crosses a predetermined per-phase threshold (not shown). In one example, the predetermined per-phase threshold may correspond to one or more of noise, interference, or sub-properties of the delta-connected capacitor bank 502. By providing an appropriate predetermined per-phase threshold, a false detection of the electrical closing time is avoided by compensating for the small magnitude of the voltage when energizing only the second switching. A similar approach can be applied to magnetically coupled reactor banks, ungrounded non-magnetically coupled reactors, etc.

[0113] 6 illustrates a method for determining an electrical turn-on time of a switching device, according to one embodiment of the present subject matter. The order in which method 600 is described is not intended to be construed as a limitation, and some of the described method blocks may be performed in different orders to implement method 600 or alternative methods. Furthermore, method 600 may be implemented in any suitable hardware, computer readable instructions, firmware, or combinations thereof. For purposes of illustration, method 600 will be described with respect to the implementation shown in FIG.

[0114] In method 600, at block 602, during energization operation of the electric equipment through the switching device, a measured terminal voltage for each of one or more phases of the electric equipment is obtained from a voltage measurement device, the phases of the electric equipment being electrically or magnetically coupled to each other. In one example, the electric equipment may be any one of a magnetic and / or electrically coupled transformer, a delta connected or ungrounded capacitor bank, a delta connected or ungrounded non-magnetically coupled reactor, or a magnetically coupled reactor. In one example, the measured terminal voltage for each phase may be obtained from a voltage measurement device connected to the load side of the switching device.

[0115] At block 604, circuit configuration parameters associated with the electrical equipment are obtained. In one example, the circuit configuration parameters may include one or more of a connection configuration of the voltage measurement device, a location of the voltage measurement device, a type of the voltage measurement device, a design characteristic of the electrical equipment, a number of windings and their connection configuration, a type of winding configuration in which controlled switching is performed, a switching sequence of the electrical equipment, and the like. The connection configuration of the voltage measurement device may refer to how the windings of the voltage measurement device are connected. For example, if the voltage measurement device is a star-grounded to delta connected potential transformer, the connection configuration of the measurement device refers to a potential transformer having a winding connected to star ground and another winding connected to delta. The location of the voltage measurement device refers to the side to which the voltage measurement device is connected. For example, if the electrical equipment is a star-delta transformer, the location of the voltage measurement device may refer to a voltage measurement device connected to the star side of the transformer or the delta side of the transformer. The design characteristics of the electrical equipment, such as a transformer, may include a core design of the transformer, how the delta connections on the windings are formed, and the like. Switching sequence refers to the order in which the poles of the circuit breakers associated with the phases of the electrical equipment are closed. The type of electrical equipment for which controlled switching is performed may be coupled loads such as transformers, capacitor banks, or reactor banks, to name a few.

[0116] At block 606, a process voltage is determined for one or more phases of the electrical equipment. The process voltage is determined based on one or more of the measured terminal voltages of the electrical equipment and a mapping table. The mapping table includes a mapping between circuit configuration parameters and calculations performed on one or more of the measured terminal voltages. In one example, the mapping table may be theoretically determined by circuit analysis.

[0117] At block 608, based on the processed voltage, an electrical closing time of a pole of a switching device associated with a phase of the one or more phases is determined to monitor the energization operation of the electric equipment. The electrical closing time of the pole of the switching device is determined at a time corresponding to the beginning of the rising slope when the rising slope of the processed voltage crosses a predetermined per-phase threshold to reach a first voltage peak. The predetermined per-phase threshold corresponds to one or more of noise, interference, or sub-properties. The sub-properties of the electric equipment may refer to design attributes of the electric equipment such as unequal flux path lengths in a three-legged core design transformer, or unequal flux path lengths in a reactor, etc.

[0118] The electrical closing time of the poles of the switching device may be determined to monitor the energization operation of the electric equipment. In one example, monitoring the energization operation of the electric equipment includes evaluating a closing time based on the determined electrical closing time of the poles of the switching device evaluated during the energization operation. The closing time of the poles of the switching device is a time from when the switching device receives a closing command to when the circuit is detected to be electrically closed through the determined electrical closing time. The evaluated closing time may be compared to an expected closing time for the obtained circuit configuration parameters to determine an error. A correction may be applied to the closing time of the poles of the switching device based on the determined error to improve the performance of the subsequent energization operation. In one example, the measured terminal voltage of any one of the one or more phases or any two of the one or more phases is used to determine a processing voltage to detect the electrical closing time of the poles of the circuit breaker associated with any other of the one or more phases based on the mapping table. In another example, if the electric equipment is inductive having a magnetic circuit, the step of determining the processing voltage may be performed by determining a winding voltage, the winding voltage generating a magnetic flux linking each phase of the electric equipment. In yet another example, where the electrical equipment is a capacitor bank, determining the process voltage may be performed by determining the voltage across an equivalent capacitance for each phase of the electrical equipment.

[0119] According to one aspect, a non-transitory computer-readable medium may be provided that includes program instructions that, when executed, cause a processor to perform a method 600 for determining an electrical turn-on time of a switching device for monitoring the energization operation of an electrical device.

[0120] Thus, the present subject matter provides a fast and accurate method for detecting the electrical turn-on instant of a coupled load in order to monitor the energization operation of the coupled load.

[0121] Although the present subject matter has been described with reference to particular embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the subject matter, will become apparent to those skilled in the art upon reference to the description of the subject matter.

Claims

1. obtaining, during energization operation of an electric device via a switching device, a measured terminal voltage of each phase of one or more phases of the electric device from a voltage measurement device, the phases of the electric device being electrically or magnetically coupled to each other; obtaining circuit configuration parameters associated with the electrical device; determining a processing voltage for the one or more phases of the electric equipment based on one or more of the measured terminal voltages of the electric equipment and a mapping table, the mapping table including a mapping between the circuit configuration parameters and a calculation performed on one or more of the measured terminal voltages; determining, based on the process voltage, an electrical closing time of a pole of the switching device associated with a phase of the one or more phases for monitoring the energization operation of the electric equipment, and determining the electrical closing time of the pole of the switching device as a time corresponding to a start of the ascending slope of the process voltage when the ascending slope of the process voltage crosses a predetermined per-phase threshold value to reach a first voltage peak; A method comprising:

2. Monitoring the energization operation of the electrical device includes: evaluating a closing time based on the determined electrical closing time of the poles of the switching device during the energizing operation; comparing the turn-on time to an expected turn-on time for the circuit configuration parameters to determine an error; applying a correction to a closing time of the poles of the switching device based on the determined error to improve performance of a subsequent energization operation. The method of claim 1 , comprising:

3. 2. The method of claim 1, wherein when the electrical equipment is inductive having a magnetic circuit, determining the process voltage comprises determining a winding voltage, the winding voltage generating magnetic flux linking each phase of the electrical equipment.

4. The method of claim 1 , wherein when the electrical equipment is a capacitor bank, determining the process voltage comprises determining a voltage across an equivalent capacitance for each phase of the electrical equipment.

5. The method of claim 1 , wherein the voltage measurement device is connected to a load side of the switching device.

6. The method of claim 5 , wherein the predetermined per-phase thresholds correspond to one or more of noise, interference, or sub-properties of the electrical equipment.

7. 2. The method of claim 1, wherein the circuit configuration parameters include one or more of a connection configuration of a voltage measurement device, a location of the voltage measurement device, a type of the voltage measurement device, a design characteristic of the electrical equipment, a number of windings and their connection configuration, a type of winding configuration in which controlled switching is performed, and a switching sequence of the electrical equipment.

8. 2. The method of claim 1, wherein the measured terminal voltages of any one of the one or more phases or any two of the one or more phases are used to determine the process voltage to detect the electrical closing instant of the pole of the switching device associated with any other of the one or more phases based on the mapping table.

9. 2. The method of claim 1, wherein the electrical device is one of a transformer, a delta-connected or ungrounded capacitor bank, a delta-connected or ungrounded non-magnetically coupled reactor, or a magnetically coupled reactor.

10. An apparatus coupled to a switching device, the apparatus comprising a processor, the processor comprising: obtaining a measured terminal voltage of each of one or more phases of the electrical equipment from a voltage measurement device during energization of the electrical equipment through the switching device, the phases of the electrical equipment being electrically or magnetically coupled to each other; obtaining circuit configuration parameters associated with the electrical device; determining a processing voltage for the one or more phases of the electric equipment based on one or more of the measured terminal voltages of the electric equipment and a mapping table, the mapping table including a mapping between the circuit configuration parameters and a calculation performed on one or more of the measured terminal voltages; determining an electrical closing time of a pole of the switching device associated with a phase of the one or more phases based on the processed voltage to monitor the energization operation of the electrical equipment; It is configured as follows: The processor, an apparatus configured to determine the electrical closing time of the poles of the switching device as a time corresponding to a start of an ascending slope of the process voltage when the ascending slope of the process voltage crosses a predetermined per-phase threshold to reach a first voltage peak.

11. To monitor the energization operation of the electrical device, the processor evaluating a closing time based on the electrical closing time of the poles of the switching device during the energizing operation; comparing the turn-on time to an expected turn-on time for the circuit configuration parameters to determine an error; The apparatus of claim 10 , further comprising: applying a correction to a closing time of the poles of the switching device based on the error to improve performance of a subsequent energization operation.

12. If the electrical equipment is inductive having a magnetic circuit, the processor determines the processing voltage by determining a winding voltage, the winding voltage generating a magnetic flux linking each phase of the electrical equipment; The apparatus of claim 10 , wherein when the electrical equipment is a capacitor bank, the processor determines the process voltage by determining a voltage across an equivalent capacitance for each phase of the electrical equipment.

13. The apparatus of claim 10 , wherein the predetermined per-phase thresholds correspond to one or more of noise, interference, or sub-properties of the electrical equipment.

14. The circuit configuration parameters include one or more of a connection configuration of a voltage measurement device, a location of the voltage measurement device, a type of the voltage measurement device, design characteristics of the electrical equipment, a number of windings and their connection configuration, a type of winding configuration in which controlled switching is performed, and a switching sequence of the electrical equipment; the electrical device being one of a transformer, a delta-connected or ungrounded capacitor bank, a delta-connected or ungrounded non-magnetically coupled reactor, or a magnetically coupled reactor; 11. The apparatus of claim 10.

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