【高壓制櫃設計】 - 高壓掣櫃之設備（一）- Vacuum Circuit Breaker（VCB）真空斷路器

香港電力公司所提供給用戶的高壓電壓一般為11kV/22kV，提供與港鐵的高壓系統為33kV專線。因此用戶端接電力公司的高壓掣櫃一般最常見為11kV高壓掣櫃。

根據末端設備需求，高壓櫃的系統電壓可以利用變壓器進一步降低至6.6kV/3.3kV供設備使用。

根據政府spec，最大的Maximum symmetrical fault level 分別假設為：

• 11kV -    380 MVA
• 6.6kV -     225 MVA
• 3.3kV -     150 MVA

高壓掣櫃（HV Switchboard）

HV Switchboard 標準：IEC 62271-200:2011

高壓掣櫃的主要設備有：

• Vacuum Circuit Breaker (VCB) 真空斷路器
• 110V DC Battery Charger 
• Battery Set 
• Digital Network Analyser (電錶)
• Measuring Current Transformer (MCT) & Protection Current Transformer(PCT) 
• Voltage Transformer 
• Protection Relay 
• Selector/On/Off Switch, Indication Lamp
• Voltage Indicator
• Pilot Wire Differential Protection Relay
• Generator Differential Protection Relay
• Test Terminal 
• Termination Kit
• Neutral Earth Resistor

高壓掣（HV Switchgear）- Vacuum Circuit Breaker（VCB）真空斷路器

VCB 標準：IEC 62271-100:2012

對於11kV制櫃VCB：

• Rated Voltage：12kV
• Rated lightning impulse withstand voltage: 75kV (Peak)
• Rated one-minute power frequency withstand voltage: 28kV
• Rated short-circuit breaking current: 20kA (3 seconds) 
• Rated short-circuit making current: 50kV
• Rated control supply voltage:  220V AC for closing 110V DC for tripping

斷路器為可移動式（four wheeled truck），具有三個不同的狀態："disconnect"、"test "和 "service"。 當斷路器處於 "test "和 "service "狀態時，斷路器內部的保護裝置阻止斷路器移動出來。斷路器移動車要有效接地。

同一rating的斷路器要相互可以替換。但不同rating的斷路器要提供有效的措施防止相互替換（在低壓系統中並無此特殊考慮）

斷路器應具有遙距控制功能，提高操作的安全性。(政府spec要求)

應具備Vacuum泄漏監測警報功能，當真空泄漏嚴重到威脅到開關設備的安全運行時，斷路器應該無法合閘。(政府spec要求)

Difference Between ACB, VCB and SF6: 

具備Interlocking Gear (聯鎖裝置)

Interlocks shall be of the mechanical or key-operated type and shall be provided to prevent the following operations: 

• (i) A moving portion from being withdrawn from or inserted into the isolating contacts when the circuit breaker is closed; 
• (ii) The closing of the circuit breaker unless the movable portion is correctly plugged in or isolated from the equipment; 
• (iii) The movable portion being withdrawn or replaced unless the circuit breaker is isolated and in the appropriate position; 
• (iv) The movable portion being plugged in without the circuit breaker tank in position; 
• (v) The circuit breaker being closed in the 'SERVICE' or 'EARTH' location without completing the appropriate auxiliary circuits; and 
• (vi) To apply an earth to busbars until all circuit breakers which can feed the busbars, are locked open.