EN
Medium Voltage Cell and Panel Test
MV cell and panel testing: contact resistance, insulation, stepped VLF tests, mechanical checks, SF6 gas and internal arc classification checks.
Medium voltage cell and panel testing verifies the electrical and mechanical integrity of metal-clad MV switchgear units — cell body, disconnector-earthing mechanism, circuit breaker, current-voltage instrument transformers and busbar system — at commissioning and periodic inspection. The cell is the openable lock of the network: a 20 µΩ rise on a contact surface or one delay in the mechanism is the sign of a fault that protection may not catch. Tests run in three windows: post-installation commissioning (SAT), in-service periodic inspection and post-fault verification.
Electrical Tests
- Contact resistance (µΩ): Breaker poles, disconnector contacts and bus joints measured with a micro-ohmmeter; manufacturer reference and phase-to-phase consistency are the criteria, with live thermal verification when in doubt (thermal inspection).
- Insulation test: Barrier and insulator resistance phase-phase and phase-earth with a megohmmeter (typically 5 kV); the polarisation index separates moisture from contamination.
- Dielectric integrity: Withstand verification within the TS EN 62271-1 rated insulation (e.g. 12/72 kV class) using stepped VLF or oscillometric partial-discharge scanning to locate weak insulation on site.
- Instrument transformers: CT ratio-polarity-saturation (knee point) checks and PT insulation-winding tests — the guarantee of protection selectivity as much as measurement (transformer inspection).
Mechanical, SF6 and Timing Tests
Motor control, spring charging times, sequential disconnector-earthing interlock logic and position indicators are exercised; breaker stroke time and contact bounce give mechanical characterisation. In gas-insulated cells, SF6 pressure-temperature compensated readings, leak-sniffer control and moisture (ppmv) measurement verify the dielectric margin per IEC 60376/TS EN 62271-203. The internal arc classification (IAC) record feeds the switch room safety plan — access distance and evacuation direction.
Relay Integration and Reporting
Tests become meaningful through the protection relay: overcurrent-earth-short-circuit scenarios and the trip chain to breaker open-close are verified end-to-end with an injection kit (commissioning). A asset-based protocol per cell — contact table, insulation curves, gas values, timing charts and photographs — is produced; any exceedance closes the report with root cause and a corrective suggestion (cleaning, retorque, overhaul, replacement). Results form the baseline for the next inspection.
Legal Basis and Outcome
The work is carried out under Law No. 6331, the High Current Electrical Installations Regulation, the Internal Electrical Installations Regulation and distributor specifications with TS EN 62271-200, the IEC 62271 series and related practice. No test is done without the dead-working procedure, arc-rated clothing and permit-to-work trio. Request a commissioning or periodic test plan for your MV panels via the contact page; this service is within our MV contracting scope.
FAQ on MV Cell and Panel Test
In three windows: post-installation commissioning (SAT) — the first verification of cell-panel-busbar joints and locking logic; in-service periodic inspection — yearly tracking of dust-moisture accumulation, thermo-mechanical loosening and mechanical fatigue; post-fault verification — integrity proof after a trip or arc event. Every measurement is compared with the previous reference; the trend warns before the absolute result does.
Contact resistance with a micro-ohmmeter (breaker poles, disconnector contacts, bus joints; phase consistency and manufacturer reference), insulation resistance and polarisation index with a megohmmeter, dielectric integrity via stepped VLF or oscillometric partial discharge scan; CT-PT ratio-polarity-saturation verification. When in doubt, a live thermal camera hunt for hot spots is added. Detailed criteria sit in our transformer-breaker test services.
Spring charging times, open-close timing charts (stroke time, contact bounce), sequential disconnector-earthing interlock logic and position indicators are exercised. In gas insulated cells the SF6 pressure is read with temperature compensation, searched with a sniffer and moisture (ppmv) measured — to IEC 60376/TS EN 62271-203 limits. The internal arc classification (IAC) record feeds the switch room access distance-evacuation direction plan.
Tests complete their meaning in the protection relay: overcurrent-earth-short-circuit scenarios and the trip chain are verified end to end with an injection kit (commissioning). An asset-based protocol per cell — contact table, insulation curves, gas values, timing charts, photo record — is produced; any exceedance closes with a root cause and corrective suggestion (cleaning, retorque, overhaul, replacement).