KR100591437B1 - 154KV (2CT, 3PT) Neutral Grounding Method - Google Patents

Abstract

The present invention relates to a three-phase power metering method in 154KV (2CT, 3PT) neutral grounding method, 2CT TTB terminal block (51) after installing the transformer current transformer 22 in addition to the neutral line without changing from the 3CT method to the 3CT method And a three-phase four-wire wattmeter 32 for 2CT.

In general, the 154KV supply method uses three-phase four-wire (3CT, 3PT) metering in principle, but some customers use three-phase three-wire (2CT, 3PT) metering method. The two-element three-phase three-wire metering method is over and underweighed due to the neutral grounding. Recently, the power business law has been revised to improve the three-element, three-phase, four-wire metering method. Therefore, the customer is asked to change to 3CT, 3-phase 4-wire metering method from electric service provider. However, if the existing faucet facility with two-element metering device is installed, the three-element metering device is accompanied by enormous cost and power failure due to additional CT installation. There is a problem in the electricity trade because it has not been improved due to reasons such as the shutdown of the facility. Accordingly, the present invention changes the CT connection structure of the 2TB TTB terminal block 51 CT and the CT connection structure of the 2CT three-phase 4-wire wattmeter 32 without the 154KV 2CT system power cut by indirectly measuring the B phase current (40). The present invention achieves the present invention by measuring three-phase and four-wire methods by measuring currents of B, C, and C. Therefore, three-phase four-wire power can be measured without change from 154KV 2CT system (2) to 3CT system (21), eliminating various civil complaints due to power trading market and insufficient error measurement, It is effective in eliminating power failures and at the same time reducing equipment costs.

Description

Method for 3Phase Power Meter of 154KV (2CT, 3PT) Grounded Neutral System}

1 is an exemplary view illustrating a three-phase three-wire and three-phase four-wire measurement method of a 154KV power receiving facility.

Figure 2a is an exemplary view explaining the 3PT and 2CT installation structure and M.TR neutral point floating operation of 154KV indoor and outdoor faucet facilities.

Figure 2b is an exemplary view illustrating the B phase load intensive use according to the load side transformer connection method in 154KV, M.TR 2CT neutral grounding method.

Figure 3a is a comparative example of the 2CT three-phase three-wire non-grounding metering method and the 3CT three-phase four-wire direct ground metering method.

Figure 3b is a comparison of the conventional weighing method and the weighing method according to the present invention.

3C is a vector diagram showing a B-phase current indirect measurement method using A phase, C phase, and N phase in the 2CT method according to the present invention.

4 is an internal structure diagram of a TTB terminal block for 2CT and a 3-phase 4-wire power meter for 2CT according to the present invention.

5A and 5B are installation diagrams of a TTB terminal block for 2CT and a 3-phase 4-wire power meter for 2CT in a 154KV 2CT neutral point grounding method and a non-grounding method according to the present invention.

<Description of the code | symbol about the principal part of drawing>

1: Instrument transformer (PT) 2, 21, 22: Instrument current transformer (CT)

6, 7: PT, CT installation structure inside and outside 10: M.TR neutral disconnector (D.S)

3, 31, 33: conventional electricity meter 32: 3-phase 4-wire electricity meter for 2CT

5: Existing TTB terminal block 51: TTB terminal block for 2CT

41, 42, 43: Principle and vector diagram 11, 12: Peripheral pressure and load side transformer

13: Consumer side generator 15, 16, 17: Example of vector current measurement by phase

40: B phase current indirect measurement CT connection structure 23, 24: Electricity meter internal CT connection structure

The present invention relates to a three-phase power metering method in the 154KV (2CT, 3PT) neutral grounding method, in particular, in addition to the neutral wire (N line) without changing from 2CT to 154KV power receiving equipment 3CT during 154KV M.TR neutral grounding operation After the installation of the transformer current transformer 22, the method for measuring the normal amount of 154KV three-phase four-wire using a 2TB TTB terminal stage 51 and 2CT three-phase four-wire wattmeter 32.

Currently, 154KV supply method is a three-phase four-wire direct grounding system, and a supply / demand contract is applied as a three-phase four-wire system in principle. I can do it. In particular, in the 154KV M.TR 2CT method (2), the primary Y-connected customers are often unable to operate the neutral point floating point in the system operation, and there is a problem of over and under metering in the three-phase three-wire metering method during the neutral ground operation. It is being born. Therefore, 3CT 3 phase 4 wire metering method (9) is not applied because 3CT method (21) entails expensive construction cost and prolonged power outage due to change of power receiving equipment and enormous loss such as operation stop of production facility. There is a problem with electricity market transactions.

1 is an exemplary view illustrating a three-phase three-wire and three-phase four-wire measurement method of a 154KV power receiving facility.

As shown in FIG. 1, the 154KV power supply system in Korea is a three-phase four-wire direct ground method, but the metering method is, in principle, 3CT, three-phase four-wire metering method (9), but 154KV neutral floating operation is possible. In other words, the customer can measure the neutral point after M.TR first Y connection and △ connection by 2CT, 3-phase 3-wire metering method (8).
In the 154KV 2CT three-phase three-wire metering method (8) described above, the primary side of the transformer (1) for the instrument is connected to the A-phase, B-phase, C-phase, and N-phase tracks, respectively. Instrument current transformer (2) is connected, and the instrument transformer (1) secondary output terminal and the instrument current transformer (2) secondary output terminal are each connected by a 3-phase 3-wire power meter (3) to measure 3-phase 3-wire It is made of a structure.
In the above-described 154KV 3CT three-phase four-wire metering system (9), the primary side of the transformer (1) for the instrument is connected to the A phase, B phase, C phase, and N phase lines, respectively, and A phase, B phase, and C phase. Instrument current transformer 21 is connected to the line on the upper side, and the secondary output terminal of the instrument transformer 1 and the secondary output terminal of the instrument current transformer 21 are connected to the 3-phase 4-wire wattmeter 31 respectively. It is composed of a phase 4 metering structure.

In particular, the 154KV supply line is composed of A phase, B phase, C phase, and N phase by direct grounding method.
Nevertheless, in the 154KV neutral grounding method, the 2CT three-phase three-wire metering method (8) installs the instrument current transformers (2) in only the A and C phases, and is used as the three-phase three-wire ungrounded metering method by the two-wattmeter method. There is a problem that the amount of power is excessively and insufficiently metered according to the load characteristics and environmental changes, and in particular, the 2CT method has a problem in that the B phase is not normally metered because there is no CT.

Figure 2a is an illustration of the 3PT and 2CT installation structure and M.TR neutral point floating operation of the 154KV indoor and outdoor faucet installation.

As shown in Fig. 2A, the 154KV power receiving facility is composed of an outdoor type power receiving facility 6 and an indoor type receiving facility 7. In case of contracting supply and demand contract with KEPCO with 2CT method, 3-phase 3-wire, and grounding operation of M.TR primary neutral point, 2CT method (2) can accurately measure 3-phase 4-wire power during neutral ground operation in system operation. none. Therefore, it is necessary to change the faucet facility to 3CT, 3 phase 4 wire metering method (9), but it is impossible to replace it practically due to the expensive construction cost and loss of tangible and intangible such as the shutdown of the production facility due to long power outage. In particular, if there is a generator 13 on the load side of the power receiving equipment, if the ground fault occurs on the 154KV primary side when the M.TR primary neutral point is floated, the ground fault relay 51N does not operate. In case of ground fault, transformer failure occurs due to insulation breakdown due to 154KV M.TR neutral point rise. In addition, the self-powered customer has a problem that the generator 13 is burned out due to the potential rise on the customer's ground side when the generator 13 is insulated (Y-wired), so when the ground fault on the transformer secondary side is not shared with the ground line. If the generator of the generator is operated in parallel with KEPCO's power system, the neutral point DS ON (10) should be directly grounded in order to prevent the supply system ripple accident in case of ground fault.

Figure 2b is an exemplary view illustrating the B-phase load concentrated use according to the load-side transformer connection method in the 154KV M.TR 2CT neutral point grounding method.

As shown in Fig. 2b, the 2CT 3-phase 3-wire metering method (8) is used, and the 154KV direct grounding system is a common ground with the faucet facility on the customer side through the processing ground, and only the ACT and C-phase 2CT methods. It is installed in (2). Therefore, if the first M.TR Y- △ connection (11) using only one of the unloading method as a single load, there is no problem, but practically impossible. Particularly, even when the secondary side is operated without a ground by the △ connection in the 154KV primary transformer Y-Δ11 method, a plurality of load side transformers 12 are installed, and the load side transformer 12 is connected to the Δ-Y connection method. According to the wiring method, even though the voltage is different, the phase is the same as the B phase of 154KV M.TR. When the load is used only in the B phase, the amount of power is not measured in the B phase, causing various problems due to the power market trading error between power generation companies.

An object of the present invention is to solve the conventional problems as described above, using the A, C, N-phase current in the 154KV 2CT power receiving equipment system to change the existing power equipment in the uninterrupted state 3CT system (21) It is to provide a measuring method that can measure three-phase four-wire power.

In the present invention as described above, the CT connection structure 40 for the B phase current indirect measurement may be performed using the CT connection inside the TCT terminal block 51 for the 2CT and the 3-phase 4-wire wattmeter 32 for the 2CT. Therefore, in the 2CT method (2), by measuring all the A, B, C phase current can be measured in a three-phase four-wire system, the object is achieved. Accordingly, according to the present invention, the first power error can be reduced to the maximum, the second, the installation method is simple, it is possible to replace the meter without a power failure, and the third can be used as it is without changing the expensive power receiving equipment can reduce the construction cost effect There is an advantage. In particular, in the 2CT three-phase three-wire metering method (8), the ungrounded method does not have a neutral wire, and thus, it is impossible to use a phase voltage between the power line and the neutral line. Therefore, there is no error in measuring three-phase power by the two-wattmeter method, but the 154KV supply method is a direct grounding method, and the KEPCO N line is shared with the customer's power receiving facility, and the 154KV power system is a direct grounding method. Many short-term insulation system facilities such as lightning arresters, transformers (Y connection), capacitors, and reactors are used. Therefore, there is no problem in three-phase metering of 2CT, three-phase three-wire ungrounded system.However, in 154KV direct grounded system, two-CT, three-phase three-wire metering method (8) has loads such as phase voltage, phase current, phase power factor, and harmonics. Depending on the characteristics, the power amount is under-metered or over-metered. Accordingly, the present invention improves the problems of conventional 2CT, non-grounding three-phase three-wire metering, and can easily achieve the object without changing the power receiving equipment with 3CT.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 3a is a comparative example of the 2CT three-phase three-wire ungrounded weighing method and the 3CT three-phase four-wire direct ground weighing method.

As shown in Fig. 3a, there is no problem in the three-phase three-wire ungrounded system as shown in the 2CT three-phase three-wire vector diagram 41 in the three-phase three-wire ungrounded method, but the neutral point (N-line) in the 154 KV direct grounded system. As a result of the use of single insulation system such as lightning arrester, transformer (Y connection), condenser, reactor, etc., the error caused by leakage current according to corona phenomenon, harmonics, and line characteristics, and the primary M. When the ground operation by TR neutral point DS ON (10), there is a problem that the power amount is not metered in the B phase due to the 2CT three-phase three-wire metering method (8). Therefore, in the 154KV direct ground system, each phase power must be measured and integrated as shown in the vector diagram 43 of the 3CT three-phase four-wire metering method.

In particular, when the three-phase three-wire ungrounded metering method shown in [Table 1] is used for the 154KV direct grounding method, the metering error occurs greatly according to the voltage, current, power factor, and harmonic variations of A, B, and C phases. In addition, according to the power usage conditions and environment, over-measurement or under-measurement error occurs due to the change in voltage and current on the B phase, and when the power factor of the A-phase power factor is good, the over-measurement power factor is bad. As a result of over and under metering, the improvement of the current abnormal metering device has emerged as an urgent problem in order to normalize the various civil litigation and power transaction market.

<Instrument error occurrence when using 3-phase 3-wire ungrounded weighing method for 154KV grounding method>

Figure 3b is a comparison of the weighing method according to the conventional weighing method and the present invention.

As shown in FIG. 3b, the three-phase four-wire power meter is measured by the three-phase four-wire power meter during the primary M.TR 11 neutral point grounding operation in the 154KV 2CT power receiving facility system. The instrument transformer (1) voltage is applied with 154KV / 110V line voltage, and the instrument current transformer (2) receives A phase, C, and phase currents and measures three-phase power by the two-wattmeter method. Accordingly, in order to measure three-phase four-wire power in the 2CT method, P3∮3W = P ₁ + P ₂ = V _a I _a + V _b I _b + V _c I _c -V _b I _n . In particular, when there is insufficient power meter according to the direction (+,-) of I _n , and there is a neutral point current (I _n = I _a + I _b + I _c ), between three-phase three-wire and three-phase four-wire Since the metering error of "-V _b I _n " occurs, it is separately installed in the electricity meter 33 neutral line, and the video current of the neutral ground line is measured and the three-phase three-wire electricity meter 3 is added to calculate the power amount. The measurement error caused by the fluctuation of current, power factor and harmonics is so large that the three-phase 4-wire power cannot be measured accurately. Therefore, in the 2CT method (2) as in the metering method 30 according to the present invention, the three-phase four-wire power amount is measured by using the B-phase current indirect measurement CT connection structure 40 using the A-phase, C-phase, and N-phase currents. do.

3C is an indirect measurement method and a vector diagram of a B-phase current using A phase, C phase, and N phase in the 2CT method according to the present invention.

In the three-phase four-wire direct grounding system as shown in the measurement example 15 of FIG. 3C, the sum of the vector currents of the A-phase, B-phase, C-phase, and N-phase is 0, and the A-phase and B-phase in the measurement example 16 The sum of the vectors of the C phase and the vector of the N phase is the same, and the sum of the vectors of the A, C, and N phases and the vector of the B phases is the same as in the measurement example (17). Therefore, the B-phase current can be indirectly measured as shown in the vector diagram 42 by configuring the CT connection structure of the input A-phase, C-phase, and N-phase output B-phase as a method for measuring the B-phase indirect current. In addition, 2CT, three-phase three-wire conventional weighing method and the weighing method according to the present invention as shown in Table 2 are as follows.

<2CT, 3-phase 3-wire conventional weighing method and weighing method according to the present invention>

4 is an internal CT connection structure of a TTB terminal block for 2CT and a 3-phase 4-wire power meter for 2CT according to the present invention.

As shown in FIG. 4 by changing from the 2CT method (2) to the 2CT TTB terminal block 51 of the B phase current indirect measurement CT connection structure 40 in addition to the existing TTB terminal block 5 by the 3-phase 4-wire metering method. Weighing method characterized by measuring the amount of three-phase four-wire power, and the internal CT connection structure 23 of the existing three-phase four-wire watt-hour meter 31, CT connection structure of the three-phase four-wire watt-hour meter 32 for 2CT (24) The object of the present invention is achieved by a metering method characterized by measuring the amount of three-phase 4-wire power by changing to).

The CT connection structure for detection on the 2CT TTB terminal block 51 is that the A-phase input is the end coil wound several times from the inside of the CT core to the outside based on the start coil K from the TTB terminal block input terminal 1S. Connect (L) to the output terminal IS, and input C phase is the end coil (L) wound several times from inside to outside of the CT core with respect to the starting coil (K) from the input terminal 3S. The N phase input is connected to the input terminal NL by connecting the end coil (L) wound several times from the inside of the CT core to the outside of the CT core based on the starting coil (K) from the input terminal NS. On the contrary, it has a CT connection structure that connects the start coil (K) end coil (L) terminal which is wound several times from the outside of the CT core to the output terminal 2S and 2L terminal, respectively.

In addition, only the internal CT structure of the existing three-phase four-wire meter can be easily changed to create a three-phase four-wire wattmeter 32 for 2CT. In this CT connection structure, the wires connected from the meter 1S terminal are wound one to three times in the direction of the bar from the inside of the phase A core, and then once or three times inward from the direction of the bar of the phase B core. Connect the same number of turns of wires to the 1L terminal, and pull the wires connected from the 3S terminal 1 ~ 3 times in the direction of the bar from the inside of the phase C core to the end of the wire from the side of the bar of the core B again. Connect the wire that is wound one to three times in the direction to the 3L terminal, and the wire that has been wound one to three times in the inward direction from the bar-like core of the B-phase core to the NL terminal. It has a wiring structure connected to it.

Figure 5a is a 2TB TTB terminal 51 and 2CT three-phase 4-wire power meter 32 in the 154KV 2CT neutral grounding method according to the present invention.

As shown in Fig. 5a, the 154KV M.TR primary Y connection, the neutral point DS ON (10) to the N-phase instrument to the A-phase, C-phase instrument current transformer (2) installed in addition to the existing ground during operation A current transformer 22 is installed to detect A-phase, C-phase and N-phase currents in the 2CT system, and the B-phase current is indirectly measured by the CT connection structure 40.The TTB terminal block 51 for the 2CT and the 3-phase 4-wire power meter for the 2CT (32) Weighing method using).

Figure 5b is a 2TB TTB terminal 51 and 2CT three-phase 4-wire power meter 32 in the 154KV 2CT neutral point ungrounded method according to the present invention.

As shown in FIG. 5B, when the 154KV M.TR primary Y connection, the neutral point DS OFF (10) is not floating, and the M.TR primary △ connection is not installed, the neutral N phase CT is not installed and 2CT is used. Leave the NS-NL terminal 14 of the three-phase four-wire meter 32 open without connecting the wires in an open state.

In this way, without changing the 154KV power receiving equipment to 3CT, the instrument current transformer 22 is additionally configured without a power failure to the M.TR primary neutral line (N line), and detects A phase, C phase, and N phase currents in the 2CT method. Indirect measurement of the B-phase current, the A, B, C phase current can be measured by the CT connection structure 40, it is possible to measure three-phase 4-wire. Therefore, according to the present invention, it is possible to simply measure three-phase four-line without reducing construction cost and power failure, and has an advantage of reducing the error rate as much as possible compared to the three-phase three-wire metering method.

As described in detail above, according to the present invention, the problem of the three-phase three-wire metering system is known to everyone in charge, the customer can adjust the phase load current and phase power factor at the customer's side arbitrarily and use the load on the B phase intensively. Therefore, there is a problem that is under-metered on the consumer side. In order to solve this problem, the electric service provider has been asked to change to 3CT, 3-phase 4-wire metering method. However, when installing a three-element metering device for an existing faucet installed with two-element metering device, enormous costs and power outages are required. As a result, there is no improvement in reasons such as the shutdown of production facilities, which causes problems in power trading. Therefore, in the 2CT system (2), after installing the additional CT (22) only in the neutral wire in the 2CT method (2) TTB terminal band 51 or 2CT 3-phase 4-wire integrated power meter 32 in the 154KV 2CT system (2) In addition, it is possible to accurately measure three-phase 4-wire integration without additional CT, which can prevent damage caused by power outages and reduce enormous costs and errors in power trade due to changes in power receiving facilities.

Claims (5)

delete In the 3-phase 4-wire weighing method without changing from 154KV 2CT neutral grounding method to 3CT power receiving facility, Configuring a current transformer 22 for the meter in addition to the M.TR primary neutral wire (N phase) for three-phase four-wire metering in a 154KV 2CT neutral grounding method; Indirect measurement of the B-phase current using the A-phase, C-phase, N-phase current in the 2CT method comprising the step of measuring the three-phase 4-wire power using the CT connection structure 40, In addition to the existing TTB terminal block (5) indirect measurement of B-phase current measurement method, characterized in that the three-phase 4-wire power amount by changing the CT connection structure (40) to the 2CT TTB terminal block (51). In the 3-phase 4-wire weighing method without changing from 154KV 2CT neutral grounding method to 3CT power receiving facility, Configuring a current transformer 22 for the meter in addition to the M.TR primary neutral wire (N phase) for three-phase four-wire metering in a 154KV 2CT neutral grounding method; Indirect measurement of the B-phase current using the A-phase, C-phase, N-phase current in the 2CT method comprising the step of measuring the three-phase 4-wire power using the CT connection structure 40, It is characterized by measuring the three-phase four-wire power amount by changing the internal CT connection structure 23 of the existing three-phase four-wire wattmeter 31 to the CT connection structure 24 of the three-phase four-wire wattmeter 32 for 2CT. Weighing method. The method according to claim 2 or 3, Instrument current transformer 22 is additionally installed on the neutral line (N phase) as the M.TR primary Y connection, and the B phase current is indirectly measured using A phase, C phase, and N phase currents. Weighing method characterized in that the metering. The method according to claim 2 or 3, When the M.TR primary △ connection or Y connection is not installed, the NS-NL terminal 14 is left open in the TTB terminal block without installing an additional current transformer 22 on the neutral line (N phase) when the neutral point is not grounded. Weighing method characterized by measuring the three-phase 4-wire power by measuring the B-phase current only with the A-phase, C-phase current.

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