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Bypass Unit

BSHD-01 - Bypass Unit


The BSHD-01 block is used in relay protection and automation circuits powered by secondary circuits of measuring current transformers of phases A and C. The block is used for contactless, by means of a triac, shunting and unloading of a controlled current circuit if its impedance at a current of 4 A is not more than 4 Ohms, and current 50 A - not more than 1.5 Ohms. A controlled current circuit can be coils of shutdown electromagnets of drives.


The application of the unit involves the use of a discrete output ("dry" contact) of an external relay protection device to control the bypass function.

The unit has a light indication: - a green LED "POWER", which lights up when the voltage at the output of the internal power source more than 12 V; - red LEDs "BYPASS A" and "BYPASS C", which are illuminated for the time between closing the triac of the corresponding phase and switching off the switch.

Technical parameters

Unit power supply: from current circuits of phases A and C through built-in current transformers
Operating current ranges of transformer windings, А (1-2) (2-4) (4-8)
Rated currents, A 1,5 3 5
Minimum current for bypass, A. 0,3
Rated control input voltage, V 24
Rated discrete input control current, mA 15
The power consumed by the indication and control elements from the current circuit, VA, not more than 1,6
Unit weight, kg, not more than 0,9
Protection degree
- block shell
- contact findings
Insulation resistance, mOhm, not less than:
- in a cold state under normal climatic conditions
- in a heated state at a temperature of 55 °C
- in conditions of high humidity 98% at a temperature of 35 °C

Electrical insulation in cold conditions under normal climatic conditions withstands, without breakdown and overlapping on the surface, between the independent (galvanically unconnected) electrical circuits of the unit, and between the same circuits and the grounding contact:

  • Test voltage AC current value of 2 kV and frequency 50 Hz - for 60 s;
  • Pulse test voltage of 5 kV amplitude, front edge duration 1,2 μs, pulse duration 50 μs and pulse period 5 s.

The number of pulses in the test - three different polarity.
Overall dimensions, mm: 140 x 72 x 161.

Parameters of thermal stability of current circuits BSHD-01

the name of the parameter Current limit values, A
for operating current ranges
(1-2) А (2-4) А (4-8) А
60-second thermal resistance 5 10 20
1-second thermal resistance 30 75 150 (200*)
0,1-second thermal resistance 60 125 250
* implemented in device BSHD-01-200