Routine Tests of Switchgear in the Factory

Short answer

Routine tests look for material or construction faults in every unit that leaves the factory, and they must not damage its properties or reliability. IEC 62271-1, 2017 edition, describes them in clause 8: wherever reasonably possible they are made at the manufacturer’s works and on every apparatus manufactured.

A type test proves the design once. A routine test confirms that this particular unit was built like the tested design. If you buy a switchgear assembly or a circuit breaker, the routine test protocol is the document that backs it.

The tests the standard requires

Clause 8.1 lists five groups, and product standards may add others when needed.

Voltage test on the main circuit

It is a dry, short-duration, power-frequency test. It is applied to each pole or to each transport unit, following the procedure of IEC 60060-1 and subclause 7.2. For sealed pressure systems, the test is made at the filling pressure for insulation. The test voltage is the rated power-frequency withstand voltage of column 2 of Tables 1 to 4 of the standard.

The standard allows it to be omitted in one specific case: when the insulation consists only of solid-core insulators and air at ambient pressure, provided the distances between conductive parts are verified by measurement. Those measurements are compared with the dimensional drawings of the type test report, which is why those drawings must carry the permitted tolerances.

Auxiliary and control circuits

Clause 8.3 groups four checks:

• Inspection and conformity with the diagrams. Materials, workmanship, finish, corrosion protection, mounting of components and space to strip multicore cables. The wiring layout is also checked, so that no edge or hot part can damage the conductors, along with the identification of terminals and wires, and that everything matches the diagrams.
• Functional tests. When the product standard requires them, they are made on all auxiliary and control circuits together with the rest of the equipment. They may be omitted if they were already made on the complete equipment.
• Protection against electric shock. Visual inspection is preferred. If it cannot confirm the electrical continuity of the earthed metal parts, the alternative of subclause 7.4.3 applies: 30 A d.c. to the earthing point, with a voltage drop of less than 3 V.
• Dielectric test. At power frequency only, 1 kV for 1 s.

Main circuit resistance

The d.c. voltage drop, or the resistance, of each pole of the main circuit is measured. The ambient temperature conditions and the measuring points must, as far as possible, be those of the measurement made before the continuous current test (the temperature-rise test of the type test). The test current must be within the range set by subclause 7.4.4.

The criterion is clear: the measured resistance must not exceed 1.2 times the resistance Ru measured before that temperature-rise test. In assemblies, the expected resistance may need to be calculated from the type tests. This is the value later compared at commissioning and during maintenance. To see how it is measured, read the contact resistance test.

Tightness

It is made at ambient temperature, with the parts, components or subassemblies at the minimum functional pressure (or density) for insulation, or above it.

• Controlled pressure systems, gas: the procedure is that of subclause 7.8.2.
• Closed pressure systems, gas: it can be made at different stages of manufacture or of site assembly. In the factory the cumulative method is preferred, and detection with a sniffer sensor is also accepted. If a leak is detected, the test is considered failed or the leak is quantified with the cumulative method. On site the sniffer is preferred, with a detector sensitive to at least 10⁻⁸ Pa·m³/s.
• Sealed pressure systems: for gas, the preferred procedure is that of subclause 7.8.4, and the alternative is a tracer-gas test with a mass spectrometer. For vacuum interrupters, the vacuum is demonstrated with a dielectric test of subclause 7.2.12, made after the routine mechanical test of the product standard.
• Liquid: with the equipment fully assembled, at normal ambient temperature. If subassemblies are tested, a final check is made on site.

For vacuum interrupters, the X-ray test is covered separately in X-radiation of vacuum interrupters.

The map of standards for primary equipment testing places this part among the others of IEC 62271.

Design and visual checks

The unit is checked against the purchase specification, if there is one. That is why the specification should be complete and in writing before the order.

The type tests that support these routine tests are in type tests of switchgear. What to include in the enquiry, routine test protocol included, is in data to specify switchgear. The inspection after transport continues in switchgear installation.

Equipment shipped in several units

When the switchgear does not leave completely assembled, all the transport units are tested separately. The manufacturer shows that the test is valid for the whole assembly, for example with the leakage rate, the test voltage or the resistance of a part of the main circuit (clause 8.1). Afterwards, the check on site completes what the factory could not test assembled.

What not to do

• Do not assume a routine test report exists: the standard does not require it unless agreed.
• Do not compare the site resistance with a value without knowing how it was measured in the factory: temperature and measuring points matter.
• Do not skip the inspection of the control circuits: this is where wiring errors are found before energizing.

When to call us

At Tiza Group we support factory acceptance tests (FAT) and site acceptance tests (SAT) of switchgear and circuit breakers, and we compare the site values with the manufacturer’s protocol. This field work is done in Colombia, or elsewhere on request. See our FAT and SAT testing service and write to us for a quote.

Related guides

• Type tests of switchgear: what is tested
• Data to specify switchgear: enquiry and order
• Switchgear installation: final inspection and data
• Commissioning standards: FAT and SAT
• Standards for substation primary equipment testing

References

• IEC 62271-1, High-voltage switchgear and controlgear - Part 1: Common specifications for alternating current switchgear and controlgear, 2017 edition, clauses 7.2.12, 7.4.3, 7.4.4, 7.8 and 8.1 to 8.6.

Frequently asked questions