Vacuum switchgear is widely used in medium-voltage distribution systems because it combines reliable fault interruption with a compact panel design and relatively low maintenance requirements. However, the term “vacuum switchgear” covers many possible configurations. A useful quotation requires more than a voltage level and quantity.
This guide explains the electrical ratings, panel arrangement, vacuum circuit breaker configuration, protection functions and project information that buyers should confirm before ordering.
What Is Vacuum Switchgear?
Vacuum switchgear is a metal-enclosed or metal-clad assembly that uses a vacuum circuit breaker as the main switching and protection device. The vacuum interrupter extinguishes the arc when the breaker opens. The complete switchgear panel also includes busbars, cable compartments, earthing facilities, current or voltage transformers, protection relays, control wiring and mechanical or electrical interlocks.
The breaker is only one part of the system. Panel construction, insulation, protection coordination and operating safety must be specified together.
Seven Ratings Buyers Must Confirm
1. Rated voltage
State the nominal system voltage and the required equipment rating. Typical projects may use 12kV, 24kV or 40.5kV class equipment. The required insulation level and local project standard should also be included.
2. Rated current
The busbar and feeder current ratings must match the continuous load, expected expansion and ambient conditions. Common values include 630A, 1250A, 1600A, 2000A, 2500A and 3150A, but the correct rating must come from the system design.
3. Short-circuit breaking current
Confirm the prospective fault current at the switchgear location. The breaker breaking capacity and the panel short-time withstand rating must be coordinated with the network study.
4. Short-time withstand duration
Specify the required current and duration instead of listing only a kA value. This affects the breaker, busbar system, earthing circuit and panel construction.
5. Power-frequency and impulse withstand levels
These values must match the system voltage, installation altitude and project specification. High-altitude installations may require special consideration.
6. Operating sequence
Protection and auto-reclosing duties affect the operating mechanism and control scheme. State whether the feeder requires manual operation, remote operation or automatic reclosing.
7. Internal protection requirements
Define the enclosure degree, segregation, interlocking and any internal-arc requirement in the project specification. Do not assume every panel with the same voltage rating has the same safety construction.
Fixed or Withdrawable Vacuum Circuit Breaker?
A fixed VCB is permanently mounted inside the panel and can be suitable for compact or cost-sensitive applications. A withdrawable VCB is installed on a truck or handcart that can move between service, test and isolated positions. The withdrawable arrangement simplifies inspection and replacement while supporting visible operating positions and interlocking.
For 40.5kV indoor distribution, review the KYN61-40.5 metal-clad withdrawable switchgear. For outdoor 35kV feeders, see the ZW7-40.5 outdoor vacuum circuit breaker and the ZW32-40.5 auto-recloser.
Protection, Metering and Control Configuration
The RFQ should define the protection relay functions, CT ratio and accuracy, VT arrangement, energy metering, trip and close coils, anti-pumping circuit, auxiliary contacts and control power supply. If the system connects to SCADA, include the communication protocol and remote-control points.
Control voltage must be stated clearly. Different projects may use DC or AC supplies for closing, tripping, spring charging, lighting and anti-condensation heaters.
Mechanical and Electrical Interlocking
Interlocking helps prevent unsafe operating sequences. A typical withdrawable panel may require interlocks between the breaker position, breaker state, earthing switch, cable compartment door and secondary plug. Buyers should provide the required operating logic instead of relying on a generic arrangement.
Information to Include in a Vacuum Switchgear RFQ
- Single-line diagram and feeder quantity
- Nominal system voltage and equipment rated voltage
- Busbar and feeder rated currents
- Short-circuit breaking current and withstand duration
- Fixed or withdrawable VCB requirement
- Protection relay functions and communication protocol
- CT and VT ratios, accuracy classes and metering scope
- Control, trip, close and motor power supplies
- Cable entry direction, cable size and number of cables per phase
- Panel dimensions or room layout restrictions
- Ambient temperature, altitude, humidity and pollution conditions
- Applicable standards, test reports and documentation requirements
- Quantity, delivery destination and required delivery schedule
Common Specification Mistakes
The most common mistake is requesting “12kV vacuum switchgear” without a single-line diagram, fault level or feeder details. Another is comparing quotations that include different relays, CTs, interlocks and accessories. Buyers should compare the complete technical scope, not only the panel price.
Replacement projects also require special attention. Provide the existing panel drawings, breaker nameplate, busbar arrangement, cable connection details and secondary wiring so that mechanical and electrical compatibility can be reviewed.
How Enertro Supports Vacuum Switchgear Projects
Enertro manufactures medium-voltage switchgear, vacuum circuit breakers and related components for industrial, utility and EPC projects. Our team can review the single-line diagram, duty requirements and installation conditions before preparing a technical proposal.
For 35kV outdoor applications, read our 35kV vacuum circuit breaker selection guide. To receive a quotation, send your switchgear specification and project requirements.