How To Choose Vacuum Circuit Breaker By Transformer Capacity?

How To Choose Vacuum Circuit Breaker By Transformer Capacity?
1. Choose the type of vacuum circuit breaker according to the cabinet type. For indoor fixed 10KV switch cabinets, most of them use ZN28 type vacuum switch, equipped with spring operating mechanism, which can be operated by AC or DC electric or manual operation; for indoor removal type 10KV switch cabinet (such as KYN type), VS1 vacuum switch can be selected, equipped with a spring integrated operating mechanism, which can be operated by AC or DC electric or manual operation;

2. Select the rated current of circuit breaker. Generally, there are four types of distribution circuit breakers: 630A, 1000A, 1250A, and 1600A. You should calculate the load current flowing through the circuit breaker according to the load condition, and then select its rated current after leaving a margin; for a 2000KVA transformer, Rated current I=2000/(1.732*10)=115.5A, 630A circuit breaker can be selected initially, but it should be checked;

ZN 63M – 12 / A – KA
ZN-Indoor Vacuum Circuit Breaker
63M- Design Number, M- Permanent magnet mechanism
12- Rated Voltage
A – Rated Current
KA -Rated short-circuit breaking current value

3. Check the breaking current of the selected circuit breaker. Calculate the short-circuit current value at the installation site of the circuit breaker and compare it with the initially selected breaking current value of the circuit breaker. After leaving a margin, the breaking current value of the circuit breaker should be greater than the maximum short-circuit current value at the installation site, so as to ensure when a short circuit occurs, the circuit breaker can operate reliably, remove the fault without being damaged. Generally, the rated short-circuit breaking current value of a 10KV vacuum circuit breaker is mostly 20KA, 25KA, 31.5KA, 40KA, corresponding to the following four rated currents of 630A, 1000A, 1250A and 1600A; if the 2000KVA transformer is installed near the outlet of the substation and the maximum short-circuit current value is 26KA, the rated short-circuit breaking current of 630A switch which is 20KA will not meet the requirements of the point for using, so, a circuit breaker with a rated current of 1250A and a rated short-circuit breaking current of 31.5KA should be chosen.

4. Check other conditions such as the distance between phases, installation dimensions, interlocking conditions, whether there is a lock, whether it is with an overcurrent coil, whether it is with a voltage loss, and so on.
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