Integrated metering and protection panel for distribution transformer

Abstract

As attached

Description

FIELD OF THE INVENTION:The present invention generally relates to metering and protection system for distributiontransformers. More particularly, the present invention relates to an integrated metering andprotection panel for distribution transformers.BACKGROUND:Electrical power distribution is the final stage of distributing electrical power from the transmissionsystems to the individual consumers by means of a distribution transformer. Initially, the electricalpower from the generating station is transmitted at a high voltage to a local substation. Thetransmitted high voltage is then stepped down at the distribution end with the help of step-downtransformer. The stepped down voltage from the transformer is sent through LT distribution lines,which are then connected to homes / businesses of the consumers.In general, the LT distribution transformer system consists of separate metering and protectioncubicle. The metering cubicle is used for recording the export energy from DistributionTransformer and for energy audit purpose and the protection cubicle is used for safeguarding fromoverload and short circuit protection. The system also employs circuit breakers and otherprotection devices to prevent damages to the transformer. All these components are present in adistribution box erected on the low tension (LT) side of the distribution transformer occupyingmuch space as the size of the box is huge.There are various existing prior art that discloses an integrated metering and protection panel fordistribution transformer. Some of the prior art are as discussed below:Chinese Patent Number 206742721 to FANG SHUAI et al. entitled "A kind of intelligentmodularized change" relates to an intelligent modular platform changeable for low-voltagedistribution networks. The intelligent modular station comprises a low voltage distribution sidewith electricity meter and protection circuit integrated together. The intelligent unit comprises alow-voltage intelligent electric leakage switch which provides indirect contact protection againsthuman electric shock accidents and also prevents equipment damage caused by the fire. A mouldedcase circuit breaker is connected to the outlet of the fuse disconnector for short circuit and overvoltage protection. The system also has double pass bushing for inserting cable which providesdustproof, waterproof and moisture proof. The system is more space-saving and the line loss issignificantly reduced improving the reliability of the power supply.Chinese Patent Numbers CN209313203, CN101651299, CN201490604 and Chinese ApplicationNumber CN109193434 deal with an integrated design of distribution box for metering andprotection panel at the low-voltage side of the transformer. The system is provided with protectionover short circuit and over load protection using circuit breaker preventing damage to theequipment. Some of the system are provided with effective door locking systems and SMS alertand warning alarm functionalities, when there is a fault situation in distribution box.Though there are various distribution transformer system integrated with both metering andprotection panel, none of them disclose the incorporation of metering and protection cubicle in asingle panel. Also, the existing systems provide moulded case circuit breaker (MCCB) for isolatingthe power supply in case of electrical faults but does not disclose any protection mechanism intripping the MCCB when there is a leakage current or insulation failure in safeguarding humanlives and for monitoring and isolating the power supply when the door of the panel is kept openfor more than the preset time.Hence, there is a need for a system that performs a tripping mechanism when the low-tensiondistribution (LTD) box door is kept open for a more than predefined time or when there is a leakagecurrent, by automatically switching OFF / isolating the power supply thereby increasing safetyinside the panel and to the humans / animals.OBJECTS OF THE INVENTION:The primary object of the present invention is to provide an integrated system with metering andprotection cubicle incorporated in a single panel for distribution transformers.Another object of the present invention is to provide an integrated system with automatic switchingOFF the power supply when the door of LT distribution box is kept open for more than the pre-settime.Yet another object of the present invention is to provide an integrated system that isolates thepower supply when the leakage current flows to the earth due to insulation failure ( i.e. Whensnapped bare conductor falls on wet ground)Yet another object of the present invention is to increase the safety on LT side of distributiontransformer.SUMMARY OF THE INVENTION:To achieve the above-mentioned objectives, the present invention discloses an integrated systemwith both metering and protection cubicles incorporated in a single panel for distributiontransformers.According to the present invention, the integrated system with metering and protection panel fordistribution transformers comprises: an enclosure fabricated with five corner profile, a meteringcubicle with a meter for recording total export energy from the distribution transformer and furtherfor energy audit purpose, a protection cubicle for protection mechanism during electrical faults, aMoulded Case Circuit Breaker (MCCB) for isolating the power supply, a Vertical Switch FuseUnit (VSFU) for providing overload or short circuit protection, an Earth Leakage Relay (ELR) formonitoring leakage current. All these components are integrated into a system and thus, saving thespace at the LT distribution side.The MCCB of the present invention automatically trips by energizing the trip coil / isolates thepower supply in certain circumstances such as when there is overload or short circuit or leakagecurrent or when the door of the Metering and Protection (M&P) panel is kept open for more thanthe pre-set time, thus increasing safety to the public / workmen and also prevents the entry ofreptiles / rodents / worms into the panel. This increases and develops a professional and safe workculture among the maintenance staff.In accordance with the present invention, a door switch is provided in the front door of theintegrated panel. The door switch continuously transmits the door open signal to the on-delay timerwhich generates the trip command if the door is kept open for more than the pre-set time.In accordance with the present invention, the integrated system is provided with a data logger forcontinuous monitoring of the input and for enabling the output as per the logger. The data loggergenerates alert and sends SMS when there is a trip in the MCCB or when the fuse blows OFF orwhen the distribution transformer oil level is low or when the oil temperature is highIn the present invention, the metering and protection cubicle are incorporated in a single panel andare directly wired, thereby reducing the length of the lead wires and eliminating dangling of wiresat the distribution transformer center. This in turn reduces the power loss, heat generation due topower loss and declining of di electric strength in the lead wire due to heat generation. In addition,the extra diameter / idle holes present on the LTD box for cable entry is fitted with P.G glands forpreventing the entry of reptiles, rodents, worms etc. inside the panel. This further prevents theseepage of rain water and also entry of moisture and dust into the panel.In accordance with the present invention, a provision for isolation of the power supply is made inthe metering and protection panel when the snapped LT conductor falls on wet ground. Thisprovides a vital protection system that helps in avoiding accidents and loss of life due toelectrocution. The provision for the vital protection system is incorporated in the integrated panel.The present invention also allows the user to display safety poster / advertisements on the frontdoor of the LT distribution box with LED lights. These LED lights are switched ON / OFF throughthe programmable digital timer.Thus, the present invention provides an accountability for the amount of units exported along withvarious protection for metering and protection cubicle for distribution transformer system. Theintegrated system with both metering and protection cubicle incorporated in a single panel,reduces the space required at distribution transformer centers thereby reducing real estate footprint, reducing the size, weight and cost of the panel.The objective and advantages of the present invention will become more evident from thefollowing detailed description when taken in conjunction with the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS:The objective of the present invention will now be described in more detail with reference to theaccompanying drawings, in which:FIG. 1 shows metering and protection cubicle integrated in a single panel;FIG. 2 shows the section front view of the integrated panel of the distribution transformer;FIG. 3 shows the interconnection of power circuit and metering circuit in a single panel;FIG. 4 shows the control circuit of metering and protection panel;FIG. 5 shows the LT distribution box incorporated with metering and protection panel;FIG. 6 shows the metering chamber of the present invention;FIG. 7 shows a display board with LED lightings displaying posters / advertisements; andFIG. 8 shows few components of the present invention.REFERENCE NUMERALS:100: Integrated system1: DTC metering and protection panel2: Energy meter3: Metering chamber4: LED lights5: Mounting clamp6: Pad locking7: Panel locking8: PG glands9: Push buttons10: MCCB11: MCCB mounting unit12: Panel handle13: Meter lock14: Bus bar supportDETAILED DESCRIPTION OF THE INVENTION:The present invention describes the incorporation of an integrated Metering and Protection cubiclein a single panel for the distribution transformer system.According to the present invention, the integrated metering and protection panel is placed on thelow tension (LT) side of the distribution transformer. The integrated metering and protection panelcomprises an enclosure having fabricated five corner profile with 2mm of CRCA sheet and iscoated with epoxy powder.The integrated system of the present invention comprises a metering cubicle with a meter forrecording total export energy from the distribution transformer and further for energy auditpurpose, a protection cubicle for protection mechanism during electrical faults, a Moulded CaseCircuit Breaker (MCCB) for isolating the power supply, a Vertical Switch Fuse Unit (VSFU) forproviding overload or short circuit protection for individual LT circuits, an Earth Leakage Relay(ELR) for monitoring leakage current. All these components are integrated into a system and thus,saving the space at the distribution side.FIG. 1 shows the integrated system (100) proposed in the present invention. The metering andprotection cubicle are incorporated in a single panel (1) for monitoring and protecting the internalcircuits from electrical faults and also for increasing the safety on the LT side of distributiontransformer. The sectional front view of the integrated distribution transformer is shown in FIG.2.The panel (1) of the present invention has a dimension of about 700mm x 415mm x 1000mm. Thesurface of the panel (1) is prepared using 7 tank process and are painted using powder coating, forexample: RAL 7032 for door and KASH GREEN for body. The powder coating on the panel (1)is about 80-microns thickness. The metering and protection panel (1) is provided with 2.5 SQMMand 1.5 SQMM PVC insulated multi strand copper wiring.According to the present invention, the lead wires are directly connected to the integrated meteringand protection panel for distribution transformer, thereby reducing the length of lead wires andeliminating dangling of wires at the distribution transformer centers. The reduction in length oflead wires reduces the power loss, heat generation due to power loss and declines the Di-electricstrength in the lead wire due to heat generation. In addition, the extra diameter / idle holes presenton the LTD box for cable entry is fitted with P.G glands for preventing the entry of reptiles,rodents, worms etc. inside the panel. This further prevents the seepage of rain water and also entryof moisture and dust into the panel.FIG. 3 shows the interconnection of components in a single panel (1). The panel (1) comprises ofa metering portion wired from a DTC meter, an Aluminum bus bar interlinked between variouscircuit terminals, a core balance current transformer (CBCT) connected with the ELR formonitoring the leakage current and this in turn is connected to MCCB (400A) (10) for tripping thecoil, if necessary. A vertical switch fuse unit (VSFU) (250A) is connected to the individual LTcircuit through lead wired for preventing the external circuits from overload or short circuit ofindividual LT circuits. The lead wire is about 1x240 sq.mm thickness and bus bar is about 60x10mm in dimension.FIG. 4 shows the control circuit of metering and protection cubicle. The control circuit is providedwith an Isolation transformer with an input power supply (433 VAC) for supplying input power tothe control transformer (CNTr) which is 440 / 210 VAC, 50 VA. In the circuit, a door switch isconnected with on-delay timer (T1) for enabling / disabling power circuit. The door switch iscontrolled by the door open timeout. When the door open time exceed the preset time a tripcommand is generated & fed to the MCCB trip coil for switching OFF the power supply. The ELRin the circuit is connected with a CBCT for monitoring the leakage current in the LT distributionsystem. The MCCB (10) is also tripped when the ELR generates a trip command. The glowing ofLEDs (D1 to D10) (4) is controlled by a real-time clock (RTC) delay timer. Push button (9) PB1is present for resetting the ELR and PB2 for testing the glowing of LED (4). The circuit is alsoprovided with a provision for future addition of trip command when oil level is low and when thetemperature of oil is high in the Distribution Transformer. The oil level in the distributiontransformer is determined by using a float switch and the temperature of the oil is determined byusing a temperature sensor.In accordance with the present invention, the power supply is automatically switched OFF whenthe door of the LT distribution box is kept open for more than the pre-set time. A door switch ispresent in the front door of the distribution box. This switch continuously transmits the door opensignal to the on-delay timer which generates the trip command if the door is kept open for morethan the pre-set time. The on-delay timer is provided with a provision to set a time delay from 1sec to 60 minutes. For example, the time delay is normally set for 5 minutes. The system alsoisolates (i.e., trips) the power supply when the snapped LT conductor falls on wet ground due torain or wind and thereby protecting the life of humans and animals from electrocution.The present invention allows displaying of the safety poster / advertising using with LED lights(4) on the display board present in the front door. These LED lights (4) are switched ON / OFFthrough the programmable digital RTC timer to save the power during daytime. The system alsoallows the user to brand the power distribution company / display the helpline telephone numberand other social media consumer redress channels. The FIG. 8 shows the door switch, push button,indication lamp and other controlling devices of the present invention.The detailed working of each element of the integrated system is explained below:Moulded Case Circuit Breaker (MCCB) and MCCB Mounting Unit:The integrated system (100) of the present invention is provided with a MCCB (10) along with atrip coil for isolating / switching of the power supply. The MCCB (10) is directly mounted on theMCCB monitoring unit (11) without bare bus bar. This unit increases the safety inside the panel(1). The outgoing terminals of the MCCB (10) are directly connected to the bus bar. The bus barhas a main interlinked connection between incoming and outgoing circuits. The suitable size ofthe bus bar is selected as required.The MCCB (10) of the proposed integrated system (100) isolates / switches OFF the power supplyduring the following circumstances, when:-the distribution transformer is overloaded-a short circuit occurs-the current is more than pre-set value-the door is kept open for more than preset time (i.e., normally 5 minutes)-the snapped LT conductor falls on wet ground-there is a manual trippingVertical Switch Fuse Unit (VSFU):The vertical switch fuse units (VSFU) of the proposed integrated system (100) provides theoverload and short circuit protection to the individual LT circuits. The integrated system (100) isalso provided with a high rupturing capacity (HRC) fuse connected in series with the line. TheHRC fuse will blow off when short circuit occurs or when the current is more than the fuse rating,thereby isolating the power supply.Door Switch and On Delay Timer:The present invention is provided with a door switch in the front door of the LT distribution box.The door switch generates the trip command when door is kept open by using an on-delay timerpresent in the integrated metering and protection panel. The on-delay timer continuously receivesthe door open signal from the door switch and generates the trip command to MCCB (10) if timedelay is more than the pre-set value. Normally, the time delay is set for 5 minutes. And, there isalso a provision for the time delay to set from 1 sec to 60 minutes.Core Balance Current Transformer (CBCT) and Earth Leakage Relay (ELR):The vector sum of the current is zero when there is no leakage current in the LT circuit. In thepresent invention, when the snapped LT conductor falls on wet ground or when leakage currentflows to the earth due insulation failure, a leakage current is generated in the CBCT. The leakagecurrent generated is then fed to the earth leakage relay (ELR) for continuous monitoring. Whenthe leakage current is more than preset value ranging from 25ma to 3000ma, the ELR generatesthe trip command to MCCB (10) in order to isolate the power supply.Double Door Locking system:The integrated system (100) of the present invention is provided with a double door lockingsystem. The locking system includes a panel locking system (7) and a pad locking system (6) forlocking the single panel (1) and the energy meter (2) respectively. During maintenance / breakdown,the MCCB is initially kept in OFF condition for creating a safety zone and also to preventswitching ON of the MCCB by any unauthorized person. The pad locking system is provided forhassle free maintenance / breakdown work on the LT side by the maintenance staff.Display Board:A display board is mounted on the front panel door of the LT distribution box. This display boardis illuminated using LED lights (4). The switching ON / OFF the LED lights (4) are controlled byreal time clock (RTC) digital timer. The switching ON / OFF timing of the light is programmed asrequired. The display printing on the board is sandwiched by acrylic sheet on both the sides.Light Emitting Diode (LED) and RTC Digital Timer:The LED lights (4) are employed for illuminating the front door advertisement display board asshown in FIG. 7. The LED lights (4) are provided with a DC power supply unit. The DC powersupply unit converts AC power into DC power for illuminating LED lights (4). The illuminationof the LED lights (4) is controlled by real time clock (RTC) digital timer. The timings areprogrammable as required such as 4 timings per day with RTC. This RTC digital timer functionsas a street light timer. The RTC works with a battery backup power supply.Indication Lamps:A LED based indication lamps are mounted in the integrated panel (1) as shown in FIG. 8. Theindication lamps are switched ON when the MCCB (10) trips for the following conditions:-When door is kept open more than pre-set time-When ELR generates the trip commandPush Button:FIG. 8 shows the Push buttons (9), PB1 is present in the panel (1) to reset the ELR and PB2 ispresent to test the LED lights (4) glowing where the RTC digital timer is disabled.Skin Top P.G Glands:The skin top P.G glands (8) are provided at the entry (i.e. bottom) of lead wires inside the panel(1) as shown in FIG. 2. This prevents the entry of moisture, dust, rain water entering inside thepanel (1) and also provides additional dielectric strength to the power system. It is also providedwith IP55 class protection. This provides more safety and long life when installed at outdoor. Inaddition, it also prevents the entry of reptiles, rodents, worms etc. inside the panel.ETV Energy Meter:An electronic tri vector (ETV) energy meter (2) with separate chamber (3) is incorporated in thepanel (1) as shown in FIG. 6. This energy meter (2) (of about 3PH / 4W) records the total exportenergy from the distribution transformer. This recorded energy is considered for energy auditpurpose. Normally, the current in the LT side of the distribution transformer is high and hencecannot be directly connected to the energy meter (2). In order to reduce the current with suitableproportion, a current transformer (CT) of about 400 / 5A, 3.7 VA is employed. Suitable CT's areprovided along with the energy meter (2) for metering purpose.Data Logger:The data logger is interfaced with various digital inputs and outputs. The data logger continuouslymonitors the status of the inputs and enables the output where the functioning of the data logger isprogrammed as required. A GPRS M-2-M SIM is inserted in the modem of the data logger. Thismodem communicates the electrical parameters to meter data management (MDM) server fromdistribution transformer center (DTC) meter. The data logger also generates alert and SMS is sentto all the concerned Operation and Maintenance staff during the following circumstances, when-the MCCB (10) trips on ELR command-the MCCB (10) trips on overload-respective phase fuse blows off-the door is kept open for more than preset time-the oil level in the distribution transformer is low-the oil temperature in the distribution transformer is highThe panel as described in the present invention, is made as per IEC-60529 and IEC61439standards. Also, the panels are painted as per IEC62262 standards and has a degree of protectionas IP54.The non-limiting benefits of the integrated system of the present invention are as below:-Requires less space at distribution transformer centers-Provides a reduction in panel size, weight and cost-The length of the lead wire is reduced and no dangling of wires is present at thedistribution transformer centres-Reduces real estate footprint and carbon footprint-Improves safety of public / workmen and protects the life of human / animals due tosnapped LT conductors on wet ground-Provides reduction in energy loss and down time, thereby providing more safety andlonger life-Supports in branding of the company / product at high level and helps in displaying of thesafety poster board / advertising board-Saves the amount expenditure towards advertising and increases revenue of the powerdistribution company-The panel has good aesthetic and has hassle-free maintenance and enables to develop goodprofessional work culture by the maintenance staff working in the power distributioncompany-Prevents accidents to public when comes in contact with the live wires and prevent theentry of reptiles, rodents, worms etc. inside the panelWhile the foregoing written description of the invention enables one of ordinary skill to make anduse what is considered presently to be the best mode thereof, those of ordinary skill will understandand appreciate the existence of variations, combinations, and equivalents of the specificembodiment, method, and examples herein. The invention should therefore not be limited by theabove described embodiment, method, and examples, but by all embodiments and methods withinthe scope and spirit of the invention as claimed.

Claims

1. An integrated system (100) for providing electric power from a distribution transformer, wherein the integrated system (100) comprises of: a. an enclosure fabricated with five corner profile; b. a metering cubicle with an energy meter (2) for recording total export energy from the distribution transformer and for energy audit purpose; c. a protection cubicle for protection mechanism during electrical faults; d. a moulded case circuit breaker (MCCB) (10) with trip coil for isolating the power supply; e. a vertical switch fuse unit (VSFU) for providing overload and short circuit protection to individual LT circuits; f. an earth leakage relay (ELR) for monitoring the leakage current generated in core balance current transformer (CBCT); and g. a display board for displaying advertisements and safety posters; characterized in that, a single panel (1) for incorporating the metering and protection cubicle; a door switch provided in the front panel (1) for generating a trip command when door is kept open more than preset time; h. the MCCB (10) is automatically switched OFF, when i. the door is kept open more than pre-set time ii. the ELR generates the trip command iii. the Short circuit and Overload occurs.

2. The integrated system (100) as claimed in claim 1, further comprises a data logger for monitoring the status of the input and enables the output, wherein the data logger generates alert, when i. the MCCB (10) trips on ELR command ii. the MCCB (10) trips on overload and short circuit iii. respective phase fuse blows OFF in VSFU iv. the door is kept open for more than preset time v. the oil level in the distribution transformer is low vi. the oil temperature in the distribution transformer is high.

3. The integrated system (100) as claimed in claim 1, further comprises an indication lamp indicating when the MCCB (10) trips.

4. The integrated system (100) as claimed in claim 1, further comprises a skin top gland for preventing entry of moisture, dust and rain water.

5. The integrated system (100) as claimed in claim 1, wherein the enclosure is provided with double door locking system.

6. The integrated system (100) as claimed in claim 5, wherein the double door locking system includes a panel locking system (7) and a pad locking system (6).

7. The integrated system (100) as claimed in claim 1, wherein the display board is provided with LED lighting system (4) controlled by RTC digital timer.

8. The integrated system (100) as claimed in claim 1, wherein the door switch command is based on on-delay timer circuit.

9. A display board provides the branding of the company and consumer grievance redressal channels.