Double-CT sampling double-outlet grounding homodyne protection system

Abstract

The utility model discloses a double-CT sampling double-outlet grounding homodyne protection system, which relates to the technical field of grounding homodyne protection and comprises a main control module, an AD sampling module, a plurality of double-CT sampling units and a switch control module. Each dual CT sampling unit is connected with an access terminal corresponding to the AD sampling module, collects zero-sequence current mutual inductance detection signals of a main incoming line and each branch outgoing line, inputs the zero-sequence current mutual inductance detection signals into the AD sampling module, and inputs the zero-sequence current mutual inductance detection signals into the main control module after AD conversion; the main control module outputs a zero-sequence differential signal to the switch control module according to the zero-sequence current detection signal after AD conversion; and the switch control module outputs tripping driving current according to the zero-sequence differential signal to drive a switch of a water suction pump station power system to trip. According to the utility model, the positioning precision of the grounding homodyne protection system and the operation stability of the system are improved.

Description

Technical Field

[0001] This utility model relates to the field of grounding zero-difference protection technology, and more specifically to a zero-difference protection system with dual CT sampling and dual outlets. Background Technology

[0002] Pumping stations typically use a three-phase power system to supply electricity to the motors. Under normal circumstances, the vector sum of the three-phase currents should be zero. However, when there is a fault or imbalance in the motor or system, an additional zero-sequence current will be generated. Therefore, a grounding differential protection system is required to ensure the normal operation of the pumping station.

[0003] However, traditional ground fault differential protection systems cannot distinguish between ground faults in the main line and branch lines; they can only issue ground fault alarms and cannot pinpoint whether the fault occurred on the busbar or a branch. Furthermore, existing ground fault differential protection systems trip the power supply as soon as a single current transformer (CT) detects zero-sequence current, resulting in weak anti-interference capabilities and failing to meet the stability and reliability requirements of pumping stations.

[0004] Therefore, how to improve the positioning accuracy and stability of the grounding zero-difference protection system is a problem that urgently needs to be solved by those skilled in the art. Utility Model Content

[0005] In view of this, the present invention provides a grounding zero-difference protection system with dual CT sampling and dual outlets. By setting bus CT and branch outgoing line CT separately, the system can distinguish between bus grounding and branch motor grounding, and improve system stability by sampling with dual CT at sampling points.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This utility model discloses a grounding zero-difference protection system with dual CT sampling and dual outlets, including: a main control module, an AD sampling module, several dual CT sampling units, and a switch control module;

[0008] Each of the dual-CT sampling units is connected to the corresponding access terminal of the AD sampling module, collects the zero-sequence current mutual inductance detection signals of the main incoming line and each branch outgoing line, and inputs them into the AD sampling module. After AD conversion, the signals are input into the main control module.

[0009] The main control module outputs a zero-sequence differential signal to the switch control module based on the zero-sequence current detection signal after AD conversion; the switch control module outputs a trip drive current based on the zero-sequence differential signal to drive the power system switch of the pumping station to trip.

[0010] Furthermore, the dual-CT sampling unit consists of current transformer a and current transformer b;

[0011] The zero-sequence current inductance detection signal includes current inductance signal a and current inductance signal b;

[0012] The zero-sequence differential signal includes zero-sequence differential signal a and zero-sequence differential signal b;

[0013] The switch control module includes relays a and b connected in series. Relay a is turned on when it receives the zero-sequence differential signal a high level, and relay b is turned on when it receives the zero-sequence differential signal b high level.

[0014] Furthermore, it also includes a dual-PT sampling unit and a zero-pressure lockout module:

[0015] The dual PT sampling unit acquires the voltage inductance detection signal of the main incoming line and inputs it into the AD sampling module. After AD conversion, it is input into the main control module. The main control module outputs a zero-voltage blocking control signal to the zero-voltage blocking module based on the voltage detection signal after AD conversion. The zero-voltage blocking module is connected in series with the switch control module. When disconnected, it prevents the trip drive current from being output.

[0016] Furthermore, the dual PT sampling unit consists of voltage transformer a and voltage transformer b;

[0017] The voltage inductance detection signal includes voltage inductance signal a and voltage inductance signal b;

[0018] The zero-pressure interlocking control signal includes zero-pressure interlocking control signal a and zero-pressure interlocking control signal b;

[0019] The zero-voltage interlocking module includes a relay c and a relay d connected in series. The relay c is turned on when the zero-voltage interlocking control signal a is high, and the relay d is turned on when the zero-voltage interlocking control signal b is high.

[0020] If the voltage inductance signal is greater than a preset threshold, the corresponding zero-voltage blocking control signal is high; otherwise, it is low.

[0021] Furthermore, the main control module sends an alarm signal to the corresponding fault lamp based on the zero-sequence current detection signal after AD conversion.

[0022] Furthermore, the AD sampling module is model AD7616.

[0023] Furthermore, the main control module signal is STM32F407ZET6.

[0024] As can be seen from the above technical solution, compared with the prior art, this utility model discloses a grounding zero-differential protection system with dual CT sampling and dual outlets. By setting dual CT sampling at the switches of the main incoming line and each branch outgoing line, it can accurately distinguish between bus grounding faults and branch motor grounding faults, greatly shortening the fault diagnosis time, reducing downtime caused by faults, and ensuring the stable and efficient operation of the pumping station. Each monitoring point is equipped with two CT current transformers, a and b. The dual CT sampling design greatly improves the system's anti-interference capability. The main control module adopts a dual-outlet design, and tripping only occurs when both trip signals are active simultaneously. Furthermore, a voltage transformer detection function and a corresponding zero-voltage interlocking module are also included, avoiding the problems of weak anti-interference capability and easy tripping affecting the efficient operation of the system caused by a single detection control signal. This utility model improves the positioning accuracy and operational stability of the grounding zero-differential protection system. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0026] Figure 1 A schematic diagram of the overall structure of this utility model.

[0027] Figure 2 This is a schematic diagram of the wiring position of the current transformer provided by this utility model. Detailed Implementation

[0028] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0029] This utility model discloses a grounding zero-difference protection system with dual CT sampling and dual outlets, including: a main control module, an AD sampling module, several dual CT sampling units, and a switch control module;

[0030] Each dual-CT sampling unit is connected to the corresponding access terminal of the AD sampling module to collect the zero-sequence current inductance detection signal of the main incoming line and each branch outgoing line, and input it into the AD sampling module. After AD conversion, it is input into the main control module.

[0031] The main control module outputs a zero-sequence differential signal to the switch control module based on the zero-sequence current detection signal after AD conversion; the switch control module outputs a trip drive current based on the zero-sequence differential signal to drive the power system switch of the pumping station to trip.

[0032] In one specific embodiment, the dual-CT sampling unit consists of current transformer a and current transformer b;

[0033] The zero-sequence current transformer detection signal includes current transformer signal a and current transformer signal b;

[0034] The zero-sequence differential signal includes zero-sequence differential signal a and zero-sequence differential signal b;

[0035] The switch control module includes relays a and b connected in series. Relay a conducts when it receives a high level zero-sequence differential signal a, and relay b conducts when it receives a high level zero-sequence differential signal b.

[0036] In one specific embodiment, it also includes a dual PT sampling unit and a zero-pressure latching module:

[0037] The dual PT sampling unit collects the voltage inductance detection signal of the main incoming line and inputs it into the AD sampling module. After AD conversion, it is input into the main control module. The main control module outputs the zero-voltage blocking control signal to the zero-voltage blocking module based on the voltage detection signal after AD conversion. The zero-voltage blocking module is connected in series with the switch control module. When disconnected, it prevents the trip drive current from being output.

[0038] In one specific embodiment, the dual PT sampling unit consists of voltage transformer a and voltage transformer b;

[0039] The voltage inductance detection signal includes voltage inductance signal a and voltage inductance signal b;

[0040] The zero-pressure interlocking control signals include zero-pressure interlocking control signal a and zero-pressure interlocking control signal b;

[0041] The zero-voltage interlocking module includes relays c and d connected in series. Relay c is turned on when the zero-voltage interlocking control signal a is high, and relay d is turned on when the zero-voltage interlocking control signal b is high.

[0042] If the voltage inductance signal is greater than the preset threshold, the corresponding zero-voltage blocking control signal is high; otherwise, it is low.

[0043] In one specific embodiment, the main control module sends an alarm signal to the corresponding fault lamp based on the zero-sequence current detection signal after AD conversion.

[0044] In one specific embodiment, the AD sampling module is model AD7616.

[0045] In one specific embodiment, the main control module signal is STM32F407ZET6.

[0046] In one specific embodiment, a grounding zero-differential protection system for a three-branch power supply system will be used as an example for illustration. Figure 2 As shown, K1 is the 10kV main incoming line switch, I01 is the zero-sequence current of the 10kV main incoming line, K2, K3, and K4 are 10kV three-way branch outgoing line switches, and the loads are 10kV motors on the three branches respectively. The dual-CT sampling unit I01-04 is set at K1-4 to sample I01, I02, I03, and I04 respectively.

[0047] like Figure 1 As shown, in a dual-CT sampling, dual-output grounding zero-differential protection system, the 8-channel mutual inductance signals (I01a, I01b, I02a, I02b, I03a, I03b, I04a, I04b) of the 4-channel (I01, I02, I03, I04) dual-CT sampling units are converted from digital signals to digital signals by an AD sampling unit (AD7616 chip), and the digital signals are transmitted to the main control module. The AD7616 channels correspond to... Figure 2 The relationship is as follows:

[0048] I01a, I01b correspond to Figure 2 The two channels of I01 (zero-sequence current of 10KV main incoming line).

[0049] I02a, I02b correspond to Figure 2 The two channels of I02 (zero-sequence current of 10KV branch-switch).

[0050] I03a, I03b correspond to Figure 2 The two channels of I03 (zero-sequence current of 10KV branch two switch).

[0051] I04a, I04b correspond to Figure 2 The two channels of I04 (zero-sequence current of 10KV branch three switches).

[0052] U0a, U0b correspond to Figure 2 The two channels of U0 are used to collect the zero-sequence voltage signal at the main incoming line switch and compare it with the preset threshold through the main control module. When the zero-sequence voltage signal is detected to be lower than the set threshold, it indicates that the external power supply voltage at the main incoming line is too low. A high level is output to the zero-voltage blocking module to avoid tripping caused by non-zero-sequence grounding, improve the stability of system operation, and reduce the maintenance and switch reset work of the staff.

[0053] The main control module uses an STM32F407ZET6 ARM microcontroller with an M4 core CPU and a maximum clock frequency of 168MHz. The CPU reads the conversion results from 10 channels via parallel SRAM (I01a, I01b, I02a, I02b, I03a, I03b, I04a, I04b, U0a, U0b). The CPU uses a timer with 64-point sampling at 50Hz. The AD result is calculated using DFT to obtain 10 RMS values ​​and 10 complex vector results. Using the dual-channel data of the conversion result, two differential data points, I0cda and I0cdb, are obtained. The zero-sequence differential equation for channel a is: I0cda = I01a + (2 / N1)I02a + (N3 / N1)I03a + (N4 / N1)I04a; the zero-sequence differential equation for channel b is: I0cdb = I01b + (N2 / N1)I02b + (N3 / N1)I03b + (N4 / N1)I04b. When I0cda > the zero-sequence differential setting, the set time length is met, and the output D01a relay is at a high level; when I0cdb > the zero-sequence differential setting, the set time length is met, and the output D01b relay is at a high level. The dual-output relay nodes are connected in series, allowing simultaneous protection of both outputs. This dual-channel mode improves the reliability of the protection. The above calculation method is merely an existing technical means that may be involved in implementing the functions of this utility model product and is not the focus of this utility model's protection.

[0054] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0055] The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A dual CT sampling dual outlet ground differential protection system, characterized in that, The utility model relates to a kind of zero sequence differential protection device for pump station power system, including: Main control module, AD sampling module, several double CT sampling units and switch control module; Each double CT sampling unit is connected with the access terminal corresponding to the AD sampling module, collects the zero sequence current mutual inductance detection signal of total incoming line and each branch outgoing line, and inputs the AD sampling module, after AD conversion, input the main control module; The main control module outputs zero sequence differential signal to the switch control module according to the zero sequence current detection signal after AD conversion; The switch control module outputs trip drive current according to the zero sequence differential signal, drives pump station power system switch trip.

2. A dual CT sampling dual outlet ground differential protection system as claimed in claim 1, wherein, The double CT sampling unit is composed of current transformer a and current transformer b; The zero sequence current mutual inductance detection signal includes current mutual inductance signal a and current mutual inductance signal b; The zero sequence differential signal includes zero sequence differential signal a and zero sequence differential signal b; The switch control module includes relay a and relay b in series, the relay a is turned on when receiving the zero sequence differential signal a to high level, and the relay b is turned on when receiving the zero sequence differential signal b to high level.

3. A dual CT sampling dual outlet ground differential protection system as claimed in claim 1, wherein, Also includes double PT sampling unit and zero voltage lockout module: The double PT sampling unit collects the voltage mutual inductance detection signal of total incoming line, and inputs the AD sampling module, after AD conversion, input the main control module;The main control module outputs zero voltage lockout control signal to the zero voltage lockout module according to the voltage detection signal after AD conversion;The zero voltage lockout module is in series with the switch control module, when disconnecting, make the trip drive current can not be output.

4. A dual CT sampling dual outlet ground differential protection system as claimed in claim 3, wherein, The double PT sampling unit is composed of voltage transformer a and voltage transformer b; The voltage mutual inductance detection signal includes voltage mutual inductance signal a and voltage mutual inductance signal b; The zero voltage lockout control signal includes zero voltage lockout control signal a and zero voltage lockout control signal b; The zero voltage lockout module includes relay c and relay d in series, the relay c is turned on when receiving the zero voltage lockout control signal a to high level, and the relay d is turned on when receiving the zero voltage lockout control signal b to high level; The voltage mutual inductance signal is greater than preset threshold value, and corresponding the zero voltage lockout control signal is high level, otherwise low level.

5. A dual CT sampling dual outlet ground differential protection system as claimed in claim 1, wherein, The AD sampling module model is AD7616.

6. A dual CT sampling dual outlet ground differential protection system as claimed in claim 1, wherein, The main control module signal is STM32F407ZET6.

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