Overview
The GND5-12 is an indoor rotary-type high voltage AC disconnector with single-sided earthing for three-phase 50 Hz systems rated 12 kV. Under voltage but without load it isolates lines, prevents mal-operation and earths the de-energised circuit, giving reliable separation from the main bus when a circuit breaker or other component is serviced.
The rotating knife and built-in earth contacts combine isolation and protective earthing in one compact frame for metal-enclosed switchgear. It is offered in two current grades — 630 A and 1250 A — with a 4 s short-time withstand current up to 31.5 kA and peak withstand current up to 80 kA.
Model Designation
The type is designated G N D 5 – 12 / □ and decoded as follows:
- G — disconnector
- N — place of use: indoor
- D — single-sided earthing
- 5 — design sequence number
- 12 — rated voltage in kV
- □ — rated current in A (630 / 1250)
Construction and Operation
- Rotary knife poles. Each pole uses a rotating contact system on support and live-part insulators to make a clear visible break in a compact indoor envelope.
- Single-sided earthing. Built-in earth contacts allow the isolated side to be earthed for maintenance safety (the D feature).
- Manual operation. Driven by a manual mechanism interlocked with the associated circuit breaker; it cannot break load or short-circuit current.
- Maintenance isolation. Provides reliable separation from the main circuit when servicing a circuit breaker or other components, protecting operating personnel.
Technical Parameters
Rated Parameters
| Item | Unit | GND5-12/630 | GND5-12/1250 |
|---|---|---|---|
| Rated voltage | kV | 12 | 12 |
| Rated frequency | Hz | 50 | 50 |
| Rated current | A | 630 | 1250 |
| Rated phase spacing | mm | 210 | 210 |
| 4 s rated short-time withstand current | kA | 25 | 31.5 |
| Rated peak withstand current | kA | 63 | 80 |
Rated Insulation Level
| Item | Unit | Between poles / pole-to-earth | Across the break |
|---|---|---|---|
| 1 min power-frequency withstand voltage | kV | 42 | 48 |
| Lightning impulse withstand voltage (peak) | kV | 75 | 85 |
Normal Service Conditions
- Ambient temperature: upper limit +40℃, lower limit −15℃
- Altitude: not above 1000 m (for higher altitude the rated insulation level is raised accordingly)
- Seismic: intensity not above 8 degrees
- Relative humidity: daily average not above 95%, monthly average not above 90%
- Site: free from fire, explosion hazard, severe pollution, chemical corrosion and severe vibration
Installation & Wiring
Installation and Mounting
Fix the disconnector frame to the cubicle mounting plane at the rated phase spacing (210 mm) through the Ø 13 mounting holes, keeping the rotating knives and single-sided earth contacts clear of obstructions. Couple the poles to the manual operating mechanism, then verify free travel and full seating of the main and earth contacts, the complete visible break, and bonding of the frame to the earth network before energising.
Outline & Mounting Dimensions
| Dimension | Value (mm) |
|---|---|
| Rated phase spacing | 210 |
| Overall width | 730 |
| Overall height | 490 |
| Frame height | 465 |
| Base section (end / pole / end) | 80 – 210 – 210 – 210 – 80 |
| Side view (width × height) | 440 × 160 |
| Top view depth | 250 |
| Mounting holes | 4 × Ø 13 |
| Min. cable bend radius | > R150 |
Selection & FAQs
Selection Guide
- Choose the rated current (630 or 1250 A); the 4 s short-time and peak withstand currents rise with the current grade.
- The D (single-sided earthing) feature provides maintenance earthing of the isolated side.
- Confirm the mechanism position and interlock against the associated circuit breaker.
Frequently Asked Questions
Q1: What does the type designation GND5-12 mean?
G is the disconnector, N the indoor place of use and D the single-sided earthing; 5 is the design sequence number and 12 the rated voltage in kV. The trailing figure gives the rated current in A (630 or 1250).
Q2: What does the GND5-12 do?
Under voltage but without load it isolates lines, prevents mal-operation and earths the de-energised circuit, giving reliable separation from the main circuit when a circuit breaker or other component is serviced.
Q3: What current ratings are covered?
Two grades — 630 A (25 kA / 63 kA) and 1250 A (31.5 kA / 80 kA), given as 4 s short-time withstand and peak withstand currents.
Q4: Can the GND5-12 break load or short-circuit current?
No. It switches circuits under voltage but without load and provides a visible isolating gap; load and fault currents are handled by the associated circuit breaker.
Q5: What is the insulation level?
1 min power-frequency withstand 42 kV between poles/pole-to-earth and 48 kV across the break; lightning impulse withstand 75 kV and 85 kV across the break (peak).
Q6: Where is it used?
For 12 kV three-phase 50 Hz indoor systems, as part of metal-enclosed switchgear or as an isolating and earthing section. See the disconnector range for related models.