VCB Selection Procedure

A sample general technical specification for VCB is given below. From the sample specification you will have to make one to suit your requirement Indoor/ Outdoor

Technical specificationfor 11kV VACUUM CIRCUIT BREAKERS

(A). 1. RATED VALUES AND CHARACTERISTICS

a. No. of Poles

b. Rated Normal current

c. Rated symmetrical short circuit breaking current (kA)

d. Rated short circuit making current.

e. Opening time and break time.

f. Closing time.

g. Degree of Vacuum maintained in the Vacuum chamber.

2. Minimum Clearance in Air :

1) Between poles

2) Between live parts to earth.

3. Whether circuit breaker is trip free.

2. Electrical service life

i) Rated current (times)

ii) Rated interruptions current (times)

3. Whether type test reports enclosed.

4. Whether the special guarantee for vacuum bottles for five years is accepted.

(B).

i) Class

ii) Rated Voltage

iii) Rated Insulation level

iv) One minute power frequency withstand voltage

v) Impulse withstand voltage

vi) One minute power frequency withstand voltage

on auxiliary wiring.

vii) Rated frequency.

viii) Rated cable charging current

ix) Rated (Single) capacitor breaking current

x) Rated small inductive breaking current

xi) Rated short circuit making current

xii) Rated duration of short circuit

xiii) Rated transient recovery current.

xiv) Rated operating sequence.

xv) Gap between the contacts in vacuum.

i) Area of contacts.

ii) The voltage to which the circuit breaker shall be

capable of withstanding indefinitely across open

contacts.

iii) Weight of Complete Circuit Breaker :

iv) Operating Mechanism of Circuit Breaker and Associated Equipment.

a) Type of closing mechanism

b) No. and type of auxiliary contacts.

(No. of spare normally open contacts and

no. of spares normally closed contacts are

to be indicated.).

c) Power requirement :

i) Closing Coil.

ii) Opening Coil

iii) Heaters at different locations (240V-50c/s AC)

v) IR values of the pole assembles with 5 KV megger

i. a. R Phase live part to body

b. R Phase incoming to outgoing terminals.

ii. a. Y Phase live part to body.

b. Y Phase between incoming to outgoing terminals

iii. a. B Phase live part to body

b. B Phase between incoming to outgoing terminals.

I think the General requirement for circuitbreakers for voltages above 1000 volts is as below . Please varify before use as this information is from my diary notes .

Indian Standard specification

ISS 13118/1991

IEC 62271-100-1/2001