VCB Mechanical Operation Checks - FAT

During FAT, there will be a Mechanical Operation Check to be done to ensure the mechanical operation and interlocking for the followings are in order :

1. VCB

a. the breaker can be racked in and out smoothly

b. when in the Connected Position : earth switch cannot be closed, control plug cannot be removed, when VCB closed - breaker cannot rack out, when VCB opened - breaker can rack out, VCB door cannot be opened

c. when in Intermediate Position : VCB cannot be closed and control plug cannot be removed

d. when in Disconnected Position : VCB door can be opened, earth switch can be closed and control plug can be removed

Note :

VCB cannot be connected when the VCB is closed, there is no control plug inserted, earth switch is closed and the door is opened.

2. EARTH SWITCH

a. it can be opened and closed smoothly

b. minimal rebounce on the blade

c. the padlock facility is provided

d. there is mechanical / electrcal interlock

3. SAFETY SHUTTER

a. smoothly open and close

b. the padlock facility is provided

c. latching facility provided

d. self-cancellation for latching facility in working condition

4. PT SHUTTER

a. smooth opening and closing

b. padlock facility provided

5. KEY INTERLOCKS

a. the key is released when breaker in disconnected position

b. VCB cannot rack in unless key is inserted

~ the above notes have been taken during my FAT at one of the well-known manufacturer of VCB in Malaysia

Pemilihan Saiz VCB

Pemilihan saiz VCB adalah bergantung kepada kadaran voltan VCB itu dan arus ketahanan VCB itu membuka litar sekiranya arus litar pintas wujud (short circuit current).
Melalui rumus

Berikut adalah nilai short circuit current yang dikehendaki oleh TNB bagi sistem bekalan elektrik di negara ini :

Oleh itu parameter VCB yang dipilih adalah seperti berikut :

Vacuum Circuit Breaker (VCB)

Vacuum Circuit Breaker (VCB) ialah salah satu alat pemutus voltan tinggi (VT). Ciri-ciri yang terdapat pada VCB adalah :

a) Menggunakan vakum sebagai medium untuk mematikan arka semasa kerja-kerja pensuisan dijalankan. Ini akan mengurangkan risiko berlakunya kebakaran.

b) Memutuskan litar dengan selamat sekiranya berlaku kerosakan / litar pintas / arus lampau.

c) Boleh membuka dan menutup litar dalam keadaan biasa dan bila berlaku kerosakan.

d) Mudah dari segi penyelenggaraan.

e) Mudah diperolehi di pasaran.

Pemilihan saiz VCB adalah bergantung kepada kadaran voltan VCB itu dan arus ketahanan VCB itu membuka litar sekiranya arus litar pintas wujud (short circuit current).