FZW28-12F/630A Outdoor High-Voltage Vacuum Load Switch, 10KV "Watchdog" Pole-Mounted Vacuum Circuit Breaker

The FZW28 boundary circuit breaker is an outdoor vacuum load switch specially designed for 10kV power distribution systems. It is mainly installed at the demarcation point between overhead lines and users, used to realize automatic isolation and location of faults, and improve the power supply reliability of the power grid.

Main Features and Functions

Applicable Systems: Suitable for 10kV neutral ungrounded systems, systems grounded via arc suppression coils, and systems grounded via small resistors.

Core Functions:

Automatic isolation of single-phase ground faults: When a single-phase ground fault occurs on the user side, it can automatically trip to isolate the faulty branch, avoiding impact on power supply in non-fault areas.

Automatic isolation of phase-to-phase short-circuit faults: It trips immediately when a phase-to-phase short circuit occurs on the user side, quickly isolating the faulty line.

Fast fault location: Only the responsible user will have a power outage after operation, and fault information can be reported to help operation and maintenance personnel quickly locate and handle the fault.

Monitor user load: Equipped with communication function, it can upload detection data to the monitoring center to realize remote load monitoring.

Structure Composition: It usually consists of two major parts: the switch body and the measurement and control unit, including external voltage transformers, built-in current transformers, CPU processors, and communication modules, etc.

Fault Handling Logic

Its fault handling method varies according to the system grounding mode and the location of the fault (inside or outside the user's boundary). The specific logic is as follows:

Single-phase ground fault:

When it occurs inside the user's boundary, for ungrounded systems or systems grounded via arc suppression coils, it trips after being judged as a ground fault; for systems grounded via small resistors, it trips before the substation protection operates.

When it occurs outside the user's boundary, the boundary circuit breaker does not operate.

Phase-to-phase short-circuit fault:

When it occurs inside the user's boundary, the boundary circuit breaker trips.

When it occurs outside the user's boundary, it does not operate.

Setting Coordination and Installation and Maintenance Key Points

Protection Setting Configuration: Its operating current and time limit need to coordinate with the substation outlet protection settings to ensure selectivity. For example, in a neutral ungrounded system, the single-phase ground operation time limit usually needs to avoid transient grounding and be later than the substation ground signal, and 6 to 8 seconds is optional; in a small resistor grounding system, it needs to coordinate with the substation zero-sequence protection.

Installation Precautions:

It can only be installed on branch lines or terminals, and must not be used in series.

It is usually installed on the pole of the 10kV overhead distribution line branch as the demarcation point with the user.

According to whether the user's service line is overhead or cable, there are corresponding specific requirements for the wiring method.

Operation and Maintenance Requirements:

It is necessary to regularly check the appearance, status, connectors, insulators, lightning arresters, and grounding devices, etc.

The controller's fault indicator light will keep flashing for 48 hours after operation, and a report should be made in time.

The cleaning and inspection cycle is the same as that of line pole climbing inspection, and replacement and maintenance should be considered after more than 10 years of operation.

Application Background and Value

The 10kV feeder overhead line has a complex structure and high failure rate. Traditional protection methods are prone to cause power outages of the whole line due to terminal faults. The application of FZW28 boundary circuit breaker can effectively isolate the fault area, narrow the power outage range, and speed up the fault recovery speed. It is one of the key equipment to improve the power supply reliability of distribution networks, especially multi-branch overhead lines.