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Differential relay BCH-2

Differential relay BCH-2

1 Purpose

The differential relay, as the two winding and three winding power transformer, and the single-phase differential protection for AC generator.

Relay can be prevented by non fault state (through the short circuit current transformer no-load closing when) the unstable transition current and the protection of non selective action.

2 Structure Overview

The relay is composed of the electromagnetic current relay DL-11 and the intermediate speed saturation converter..

Relay with winding short circuit, which constitutes the differential relay of some main technical properties, such as DC bias magnetic properties eliminate unbalanced current effect on the self coupling converter performance.

Velocity saturation of all windings of converter is made with a tap, so that you can step by step adjustment parameters of the relay.

When the BCH-2 type relay protection of power transformer, balance coil number of turns according to such conditions to choose, that when crossing the short circuit, the number of turns of the winding should be equal.

When protective relay for two winding transformer, the operating current can be adjusted in a range of more detailed, because in this case, we can use two balance winding.

Converter and the actuating element on a housing, in order to facilitate the separate adjustment and calibration test converter characteristics of actuator needs, executive element coil and a current transformer secondary winding, the balance winding and the working winding is through the connection plate are connected with each other, so that it can be in the test and adjustment to connect or disconnect the corresponding circuit.

Don't change the position of the pointer on the relay brand name (don't leave the name scale) or move the spring fixed screw without moving the pointer.. Doing so will deteriorate avoid magnetizing current or unbalanced current non periodic components affect the ability or reducing the relay when the short-circuit protection in the area of reliability coefficient. Converter wiring diagram 1, and its protection three windings power transformer relay external wiring diagram as Figure 2.

Figure 1

Figure 2

3.1 rated current 5A, rated frequency 50Hz. 3.10 when the number of turns of each winding is connected, the short-circuit winding is connected in A-A position, and their impedance is shown in Table 1.

Figure 3 DC flux characteristic curve

3 technical data

3.1 rated current 5A, rated frequency 50Hz.

3.2 relay start is 60 + 4 ampere turns.

DC additional magnetic characteristic curve of the 3.3 relay (Figure 3) - =f (K) should be piecewise adjustment;

The ratio of K- DC component to AC action value.

E - with the DC component, the ratio of AC current AC current relay action action and no DC component of the.

Figure 3 shows the when winding short access to different number of turns of epsilon = f (k) curve clusters, when K=0.6, corresponding the short circuited coil tap, epsilon value shall comply with the following provisions:

Short circuit winding tap position: e: A-A, 1.6 + 0.13 + 0.24; B-B, 3; C-C, 5 + D-D, 7 + 0.38; 0.56;

3.4 safety factor shall be not less than 1.35, reliable coefficient determined in accordance with the following method: relay action current ID correspondingly executes element type dl-11 relay action current I1; then turn pointer tightening hairspring, 5Id, measured elements in the corresponding action current i5 executive the action current of the differential relay, according to the following calculation obtained reliable coefficient:


3.53 times the action current, the action time of the differential relay is no more than 0.035s;

3.6 when the voltage is less than 220V, the electric current does not exceed 2a, relay contacts breaking capacity has the 50W sense load (time constant of 5 x 10-3s) circuit in DC.

3.7 in the rated current when relay balance winding (1 or 2) and the working winding turns all access, relay for single-phase power consumption should be not more than 16VA. .

3.8 ambient temperature is 40 DEG C, relay coil and a balance winding should be long-term by current of 10a, the temperature rise should not be more than 60K.

3.9 dielectric strength: part of the relay circuit metal charged foreign Lufei should AC voltage tolerance 50Hz, 2KV 1min without breakdown or flashover.

3.10 when the number of turns of each winding is connected, the short-circuit winding is connected in A-A position, and their impedance is shown in Table 1.

Wound group

The following current values (A) and impedance Z(Ω)

DC resistance(Ω)














3.11 relay weight no more than 4KG

3.12 relay winding data see Table 2

Wound group

Winding data





Wy=19Turn (each)Φ1.56

Short circuit (Zhong Zhu)


Short circuit (side column)




DL - 11 - type relay


Two coil parallel

3.13 relay appearance and opening hole size see BCH-1 type.

4 ordering information

In the order sheet should be indicated:

4.1 type and name of relay.

4.2 wiring mode (front or rear connection).

4.3 order quantity.

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