How to wire distance protection current transformers

The secondary wiring method of the current transformer.

1) When the transformer is wired by Y-11, there is 30 between the currents on both sides. The phase difference, that is, the current on the low-voltage side of the same phase is ahead of the current on the high-voltage side 30. In order to eliminate this unbalanced current, the secondary side of the current transformer for differential protection should be Y-wired, as shown in Figure 2.

The low-voltage side of the transformer, that is, the primary coil of the secondary side is connected, and the secondary wiring of the corresponding low-voltage side current transformer should be connected into a Y type. If the current transformer is polarity reduced, and it is assumed that the bus side is positive, the positive terminals of the current transformer are connected together as a neutral wire. The secondary pinout wires are connected to the negative terminals of A, B, and C respectively.

The high-voltage side of the transformer is the primary side of the primary coil is connected into Y, then the secondary wiring of the corresponding high-voltage side current transformer should be formed, and the negative terminal of the A-phase current transformer is connected with the positive terminal of the B-phase current transformer, and the A-phase line current is drawn; After the negative terminal of phase B is connected with the positive terminal of phase C, the current of phase B is drawn; After the negative terminal of phase C is connected to the positive terminal of phase A, the current of phase C line is drawn. According to the current phase relationship, the vector diagram is made, because the secondary line current of the two groups of current transformers is in the same phase, if the influence of other factors is not considered, the current of each phase into the differential relay should be 0.

2) The general overcurrent protection only depends on the action time limit to obtain selectivity, but for the double-sided power supply line and ring network, can not meet the requirements of selectivity, in order to achieve the selectivity of protection, the installation of a direction element on each current protection constitutes the direction of overcurrent protection.

The direction element can reflect the power direction, when the power flows from the bus to the line (short circuit at point D1), the power direction is "positive", and the protection action; When the power flows from the line to the bus (short circuit at point D2), the power direction is "negative", and the protection does not operate. For the zero-sequence direction protection and distance protection selected for the 110 kV line, the polarity of the current transformer is closely related to whether the device can operate correctly after operation.

The experimental report of the newly installed equipment, often all kinds of experimental technical data are very complete, all the experiments are qualified, but there is no record of current transformer polarity and wiring, due to the lack of careful acceptance work, and some errors in the polarity and wiring of the current transformer, it is not easy to be found, and the result is that after the equipment is running, the problem is exposed under a specific condition, resulting in protection misoperation or rejection.

Wiring method of current transformer:

1 One-phase wiring.

The current passed through the current coil of the wiring method reacts to the current of the corresponding phase of the secondary circuit. It is usually used in load-balancing three-phase circuits such as low-voltage power lines to measure current, electrical energy or to connect to load protection devices.

2 Two-phase V-wiring.

This wiring method is also known as two-phase incomplete star wiring. In relay protection devices, it is called two-phase two-relay wiring. In the three-phase three-wire circuit with no grounding at the neutral point, it is widely used to measure three-phase current, electric energy and overcurrent relay protection.

The current on the common line of the two V-shaped wiring reflects the phase current of the phase where the current transformer is not connected.

3. Two-phase current difference wiring.

In protective relay devices, this wiring is also known as two-phase one-relay wiring. This wiring method is suitable for overcurrent relay protection in the three-phase three-wire circuit where the neutral point is not grounded. The current current value on the public line on the secondary side of the current transformer is the root number three of the phase current, note:

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4 Three-phase star wiring.

The three current coils in this wiring mode just reflect the current of each phase is widely used in the I-phase four-wire system where the load is generally unbalanced, and also in the three-phase three-wire system where the load may be unbalanced, for the purpose of three-phase current, electric energy measurement and overcurrent relay protection.

The types of current transformers are classified in different ways.

1. Classification according to insulating medium.

1. Dry-type current transformer: It is made of ordinary insulating materials and is treated with impregnated paint as insulation.

2. Pouring current transformer: current transformer cast with epoxy resin or other resin mixed materials.

3. Oil-immersed current transformer: insulating paper and insulating oil are used as insulation, generally outdoor type.

4. Gas insulated current transformer: the main insulation is composed of gas.

Second, according to the installation method.

1. Through-type current transformer: used to pass through the screen or wall.

2. Pillar type current transformer: installed on a flat surface or pillar, and used as a current transformer for the primary circuit conductor pillar.

3. Sleeve type current transformer: a kind of current transformer directly mounted on the insulated sleeve without a primary conductor and primary insulation.

4. Busbar current transformer: a kind of current transformer that does not have a conductor but has a primary insulation, and is directly set on the bus.

1》The power cord can pass through from the P1 or P2 side of the transformer (the ammeter is not divided into each other), S1 and S2 are connected to the two terminals of the AC ammeter, and the secondary line is grounded or not grounded has no effect.

2》P1 and P2 are the threading surface of the guide power cord, for the wiring of the watt-hour meter, the power cord is different from the P1 or P2 side, and the wiring position of S1 and S2 in the watt-hour meter is also different, otherwise it will lead to retrograde. For the ammeter, the threading direction and the S1 and S2 wiring positions are not separated from each other, and the current value can be indicated normally.

1.Determine the current direction of the load. With the mains as positive, it flows to the equipment load.

2.The current direction is consistent with the actual situation, and the transformer is socketed on the corresponding circuit. Ensure that the threading direction of the transformer is consistent.

3.The IA(S1), IB(S1) and IC(S1) ports on the transformer are connected to the 1, 3 and 5 ports of the watt-hour meter with square power cords, respectively. Separately disassemble the connecting pieces between the number terminals, and the basic wiring is 1 connected to phase A current transformer, S connected to phase A current transformer, S connected to phase A power supply, number end connected to phase B current transformer S1, S2, 5 connected to phase B power supply, and the number end is connected to phase C current transformer S1, S2, 8 connected to phase C power supply respectively; 10 connected to the neutral line.

The principle of current transformer (CT) is based on the principle of electromagnetic induction, which is composed of a closed core and winding. Its primary winding turns are very small, and the string is in the line of the current that needs to be measured, so it often has all the current of the line flowing through, and the number of secondary winding turns is relatively large, which is connected in series in the measuring instrument and the protection circuit, and when the current transformer is working, its secondary circuit is always closed, so the impedance of the series coil of the measuring instrument and the protection loop is very small, and the working state of the current transformer is close to a short circuit.

The principle of the current transformer is based on the principle of electromagnetic induction. A current transformer is made up of a closed core and windings. It has a small number of turns in the primary winding and is strung in the line where the current needs to be measured, so it often has the full current of the line flowing.

The number of turns of the secondary winding is relatively large, connected in series in the measuring instrument and the protection loop, when the current transformer is working, its secondary circuit is always closed, because the impedance of the series coil of the measuring instrument and the protection loop is very small, and the working state of the current transformer is close to short circuit.

Current transformers are common electrical components in power systems, which are used to convert high-current signals into low-current signals for easy reading and monitoring by consumers. During the use of current transformers, the correct wiring method can ensure their normal operation, so as to avoid accidents and losses caused by possible rollover due to miswiring errors. The following is the wiring method of the current transformer.

1. Wiring method of a single current transformer.

The wiring method for a single current transformer is usually to connect it to a measuring device so that it can be converted into a readable signal. The specific wiring method is as follows:

1.Connect the output of the current transformer to the ground to ensure the safety of the circuit.

2.The output of the current transformer is connected to the input of the measuring device in order to transmit the measurement signal.

3.When wiring, attention should be paid to the rated capacity of the current transformer, and the principle of not exceeding its rated capacity should not be exceeded.

Second, the connection method of multiple current transformers.

When multiple current transformers need to be used, the wiring method will be slightly different and special attention is required. Here's how to wiring multiple current transformers:

1.The output terminals of each current transformer are connected in parallel to form an overall circuit mountain.

2.The formed overall circuit is connected with the grounding wire to ensure the safety of the circuit.

3.The output of the formed integral circuit is connected to the input of the measuring device in order to transmit the measurement signal.

4.The location and number of each current transformer should be clearly marked during wiring to facilitate subsequent maintenance and management of the shuttle chain.

3. Wire installation method of current transformer.

In addition to the wiring method, the wire installation method of the current transformer is also a key link. Here's how to install the current transformer wire:

1.The wires used in current transformers should have high electrical conductivity and corrosion resistance to ensure the accuracy and long-term stability of signal transmission.

2.The length and diameter of the wire must meet the requirements and must not limit the transmission and measurement range of the signal.

3.The wiring part of the wire should be safe and firm to prevent accidents and losses caused by loose wires.

Conclusion The correct wiring method of the current transformer and the installation method of the wire are important factors to ensure the normal operation and maintenance of the circuit. Attention should be paid to safety and accuracy when carrying out wiring and wire installation to ensure the smooth, safe and reliable operation of the power system.

The wiring method steps of the current transformer are as follows:Operating environment: chain chongzheng current transformer, electric meter, yellow, green and red three lines, blue line, two zero lines.

1. Install the yellow, green and red lines in turn.

2. Install S1 and S2 into the hole.

3. Continue to install the blue line of the jury separately.

4. Finally, install the red line.

5. Thread the three canopy lines through the three holes.

6. Install two neutral lines.

7. Done. <>

Summary. There are several wiring methods for current transformers: The wiring method of a single current transformer can only reflect the case of single-phase current, and is suitable for situations where one-phase current or three-phase load balance needs to be measured12.

Three-phase full star wiring and triangular wiring can accurately understand the changes of three-phase load in a timely manner, and are mostly used in transformer differential protection wiring12. The two-phase incomplete star wiring form is used the most in practical work, which saves a current transformer, and uses the combined current of phase A and C to form an inverted phase B phase current 12. The two-phase current wiring form is also only used in the three-phase three-wire circuit, and the advantage of this wiring is that not only a piece of current transformer is saved, but also a relay can be used to reflect various phase short-circuit faults in the three-phase circuit12.

Other wiring methods, such as primary side series, secondary side series, primary side series, secondary side parallel, primary side parallel, secondary side series, primary side parallel, secondary side parallel, etc.1. I hope it can help you and I wish you a happy life.

Wiring method of current transformer Hello dear! We're happy to answer for you!

There are several wiring methods for current transformers: The wiring method of a single current transformer can only reflect the case of single-phase current, and is suitable for situations where one-phase current or three-phase load balance needs to be measured12. Three-phase full star wiring and triangular wiring can accurately understand the changes of three-phase load in a timely manner, and are mostly used in transformer differential protection wiring12.

The two-phase incomplete star wiring is the most used in practical work, which saves a current transformer and forms an inverted phase B phase current 12 with the resultant current of phase A and C. The two-phase phase current wiring form is also only used in the three-phase three-wire circuit, and the advantage of this wiring is that not only saves a piece of current transformer, but also can use a relay to reflect various interphase short-circuit faults in the three-phase hand number posture circuit 12. Other wiring methods, such as primary side series, secondary side series, primary side series, secondary side parallel, primary side parallel, secondary side series, primary side parallel, secondary side parallel, etc.1.

I hope it can help you, and I wish you a happy life.