In normal operation the device does not change the network configuration. On a single-phase
ground fault, the grounding transformer provides an artificial neutral, the resistor is switched in,
the fault current is limited to the design value, and a zero-sequence signal is sent to the protection
relay for fast faulted-feeder selection and tripping - preventing sustained burning of cable and
equipment insulation.
- first impression
open - proof of content
Overall view with the doors open. The single-line diagram and secondary schematics are kept in the
upper document area, the resistor unit and analog meter sit in the middle, and the control devices
and terminal blocks are mounted on the inside of the right-hand door. Copper braid provides a reliable
ground connection, and power and signal wiring run in separate zones for easy on-site circuit tracing
and testing.
Internal layout - power train
Full internal layout. The resistor tiers on the left are stacked in layers on red epoxy post insulators
with copper busbar take-offs; the cast-resin grounding transformer on the right is carried on a blue
base frame, with HV bushings for outgoing connections. Two exhaust fans are mounted at the cubicle
roof, the disconnector operating mechanism and drive linkage sit in the middle, and copper-tube
grounding down-leads run the full height of the cubicle.
Grounding transformer - core component
The cast-resin dry-type grounding transformer. Four HV bushings lead out, with yellow, green and red leads
marking phase sequence; copper busbars connect to the cubicle grounding system. Warning labels and the
nameplate are fitted to the body, the blue base provides vibration-damped mounting, and the fully
encapsulated winding is moisture-proof, flame-retardant and maintenance-free.
Resistor stack and busbar - current capability
Close-up of the resistor stack and main-circuit busbars. Resistor grids are assembled in groups and
separated tier by tier by red insulators; tin-plated blue busbars link the tiers and lead to the current
transformers and the grounding terminal. Bolted contact faces are tightened and phase marking is
clear, balancing continuous current capacity with short-time withstand.
Resistor unit and meter - measurable
Close-up of the resistor unit and measuring devices. The disconnector contacts and insulators sit at the
top, an analog ammeter in the middle monitors resistor-circuit current, and the current transformers and
busbar connections are below. The resistor enclosure is suspended on insulators to maintain insulation
clearance to ground and cooling space.
Control panel
Door-mounted control circuit - protection logic
Control circuit on the inside of the door panel. The ZK intelligent control and acquisition module and the
terminal blocks are on the left, the BWD microprocessor-based protection (temperature control) device in
the middle, and the 2S and 1S auxiliary relays, HR2 and HR indicator lamps, SA selector switch and HG
indicator lamp follow to the right. Circuits are clearly labelled and plug-in wiring simplifies replacement.
Document compartment - compliance and traceability
Delivery
Each cubicle is fully primary- and secondary-wired and routine-tested - insulation resistance and
power-frequency withstand voltage tests - before shipment, and is supplied with the single-line diagram,
secondary schematics, terminal block diagram and factory test report. The on-board document compartment
keeps everything within reach for on-site maintenance.
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