Electrical Testing, Importance and Types

In a way to reduce electrical shock and other hazards, electrical installations undergo safety tests.

This is to ensure they conform to the safety standards set by the International Electrotechnical Commission (IEC).

The body recommends electrical testing on products and homes that use electricity, to make sure they are safe.

Some of the recommended tests include:

  • Earth
  • Continuity
  • High voltage test
  • Polarity testing
  • Fault-loop impedance
  • Current leakage test
  • Insulation resistance
  • RCDs testing
  • Functional test.

Importance of electrical testing

It helps to:

  • point out the condition/deterioration of the electrical system
  • Identify possible electric shock or fire hazards
  • Find any circuits or equipment that is overloaded
  • Save our appliances from damage.

Types of electrical testing

Electrical testing is being carried out by a qualified electrician with relevant equipment. The test is divided into two.

  • Visual inspection
  • Measurement.

Visual inspection

This is the first step in testing electrical equipment. During this stage, the electrical inspector checks the wiring system, and the outlets to make sure they conform with the stringent requirements.

They also check for earth rod, protective devices like circuit breakers, GFCIs, fire barriers, sockets and switches to make sure they are present with no visible damage.

Measurement

After visual inspection, measurements follow. Below is the test under measurement :

Continuity testing

This is usually the first test to do when inspecting electrical wiring. The inspector checks all connections with his tester to make sure there is no break up along the power system.

High voltage test

This is a general test which electrical products pass before use. During the test, the device passes through a higher voltage, about twice the operating voltage. They must withstand or pass the test with no defect on the insulated parts.

Earth testing

This test measures the resistance between the earth and the metallic body of the electrical product. A resistance of 0.5 ohms is good, but some standards specify 0.1 ohms.

Earth continuity tests help to check if a product will cause electric shock when there is insulation failure. They do the test at a higher voltage, about 25 – 60 A, using a multimeter or other testing kit.

Polarity test

Polarity tests show the various terminals in a circuit (i.e., positive, negative, and neutral). This helps to check for the wrong connection. If you switch the neutral of a circuit with a single-pole switch, the circuit will seem to be dead while it is alive.

Polarity tests ensure the switches are connected to the current-carrying conductor, and not the neutral wire.

Insulation resistance test

This test ensures the insulation of the cable is ok and has no faults. The test measures the insulation resistance between the live wires and earth.

During the test, all installations, equipment and lamps must be OFF, to ensure an accurate reading. While the circuit breakers, switches and fuses should be ON.

Depending on the size of the electrical system, a test voltage of 250, 500 OR 1000 V is supplied to it. But for single-phase supply, a test voltage of 500 V can be served.

The resistance values should be 0,25 MΩ for 250 V, 0,5 MΩ for 500 V, and above 1 MΩ for 1000 V test voltage.

Current leakage test

The current leakage test helps to check the amount of leakage current that flows through the surface of the insulator. The maximum acceptable limit for a leakage current is 210 microamperes.

Prospective short-circuit test   

Reason for testing: To ensure that in the event of a short circuit, the cable can carry enough faulty current to trip the miniature circuit breaker or blow a fuse within the stated time.

Fault-loop impedance test

The test helps to check if an electrical system will disconnect from the supply at the specified time when a fault occurs.

GFCI or RCD testing

The GFCI or residual current device (RCD) is a fast-acting circuit breaker that shuts off power once it senses current leakage.

This outlet trips OFF the current whenever it detects even small currents that cannot trip circuit breakers. Testing the receptacle involves checking the tripping time by passing a faulty current (overcurrent) through it.

Electrical Installation Condition Report

This is a report the testing officer issues at the end of the test. The report shows the details of the test. Including any observed defects, deteriorations, dangerous conditions, and any non-compliance with the National Electrical Code.

If there is any danger or potential danger, the overall state of the electrical installation will be declared unsatisfactory, and will require immediate action to remove the risk.

Below is how they classify the fault

  • C1 – Danger present, instant correction required.
  • C2 – Potentially dangerous – urgent corrective action required.
  • C3 – Need improvements.
  • FI – further investigation required.

Frequently Asked Questions

1 What does an electrical inspector look for?

Electrical inspectors check the whole installation, the wiring system, and the equipment to make sure they are standard. They also check for protective devices like circuit breakers, fuse, GFCI, and other equipment to make sure they are present.