The current transformer plays an important role in the power system. It can convert large current into small current, isolate the secondary circuit connected to relays and measuring instruments from the high voltage system of the primary current, and effectively convert the primary current into 5A or 1A, the two common standard secondary current values. When we use the equipment, we should master its wiring form. Today, Xiaobian shares several common wiring forms for your reference and learning.

The connection method of the current transformer is not complicated, and there are four common types of connection. The details are as follows:

1, single wiring form.

This connection form can only reflect the situation of the single-phase current, so it is only suitable for measuring the one-phase current or three-phase load balance, through the measurement of the one-phase situation can know the three-phase situation, so it is most of the time used for ammeter wiring.

2, three-phase complete star wiring and triangle wiring form.

Connecting the transformer can let the user timely understand the specific changes of the three-phase load, so the three-phase complete star wiring and triangle wiring are generally suitable for transformer differential protection wiring.

If the three phase full star connection is used alone, it can be used to collect meter current data in a neutral direct ground system. The wiring form of three-phase triple relay is mainly used in the neutral direct grounding system, which can be used to protect phase-to-phase short circuit and single-phase grounding short circuit. This is because this wiring form can not only reflect the phase-to-phase short circuit between various types, but also reflect the single-phase grounding short circuit.

3, two phase incomplete star wiring form.

The two-phase incomplete star connection is frequently used in practical work. It can effectively save A transformer and form the reverse phase B current by synthesizing the current in phase A and C.

Two phase double relay wiring form can not be well used to reflect the interphase short circuit, but it can not be used to fully reflect the single-phase grounding short circuit, so it is not suitable for use as a single-phase grounding protection. This wiring form is generally suitable for the neutral point is not grounded system or through the arc suppression coil grounding system, in order to do interphase short circuit protection.

4, two phase current wiring form.

This kind of connection form only for three-phase three-wire system circuit, the neutral point grounding, and generally do not have to be neutral, highlight the advantages of this connection type is that it cannot be used to save the transformer, and only need a relay can reflect the interphase short circuit fault problems in three-phase circuit, that is to say, It can use fewer relays to complete the three-phase overcurrent protection, thus helping the user to save costs.

When the fault form is not the same, its sensitivity is often different, so most of this wiring form is used for 10kV and 10kV below the distribution network as the protection of short circuit between phases, because its protection function sensitivity is relatively low, in modern has been rarely used.

It can be known that the current transformer has four connection forms, each of which has its own advantages and disadvantages. When choosing the connection form, we need to determine the connection form according to the actual working conditions. If the connection form is wrong, it may cause serious consequences.