Electricity-related deaths are on the rise. Electrical faults have caused loss of life and property.

Electrocution claims thousands of lives annually with several cases unreported and without proper investigation. It is unfortunate that standards of the electrical installation by the utility and local installers are deteriorating every day. This makes the electrical installations unsafe to property, humans and animals.
Attention is required by Energy and Petroleum Regulatory Authority (EPRA), National Construction Authority (NCA) and possibly law enforcement agencies to control or weed out the unqualified electrical installers and maintain a high standard of safe electrical systems installations for domestic, commercial, and industrial and explosive/hazardous environment applications.

To help avert electricity-related dangers and losses, it is essential to carry out periodic electrical safety audits for domestic, industrial, commercial, and explosive environment facilities.

Electrical safety audit checks whether the electrical structure of the installation meets all requisite standards. In addition, it also queries if the structure is safe for staff and in sound condition to guarantee uptime of the entire plant. The standards to meet include BS 7671 wiring regulations, IEC 60079-17 for electrical equipment in explosive areas, as well as relevant NFPA 70E requirements for electrical safety in the work places. Local standards such as, Occupational Health and Safety Act, 2007 also have to be met.

Electrical safety audit involves carrying out detailed inspection of the electrical structure. Usually this includes both the wiring and the protection switchgear in place. It involves testing and inspecting the electrical structure at normal plant operating condition. This is important because it helps to determine wear and tear. Similarly, it provides information necessary for carrying out predictive maintenance.

Typical Scope of Electrical Safety Audit Study

1. Verification of statutory compliance with respect to BS7671 and Kenyan Standards
2. Assessing the integrity of insulation of cables by carrying out insulation resistance tests
3. Taking thermal images to identify areas within the installation that have hot spots. For example, hot spots can be present in a system due to loose connections or overloaded cables.
4.  Physical inspection to identify electrical hazards  such as shock, fire, explosion, and overloading. We consequently suggest electrical safety solutions.
5. Assessing plant lightning protection system by checking the need, adequacy and maintenance of the installation.
6. Review of hazardous area classification and selection of flameproof electrical equipment in the plant. Additionally, we check maintenance aspects (if applicable).
7.  Review of the earthing system (installation & maintenance aspects), including sample earth resistance tests
8. Identifying areas of overloading. Done by carrying out load current measurements and comparing against cable current carrying capacity.
9.  Assessing electrical preventive maintenance system like tests, documentation, history cards, etc.
10. Review of the importance given to electrical safety in the company safety policy, safety committee, continuous electrical risk identification, etc.

Important Tests While On an Electrical Safety Audit

Insurance carrier estimates that nearly 25 per cent of all electrical failures are attributed to faulty electrical connections and overloads. Therefore, many insurance firms are the driving force behind requiring facilities to conduct annual electrical safety surveys failure to which compensation losses are declined. An electrical safety audit is an activity to examine the electrical installation’s suitability for continued use. Electricity drives the business effectively at the same time we cannot ignore the dangers involved in its use because, Electricity cannot be smelt, heard or seen.
Electrical Safety Audit brings out the non-compliances of an Electrical installation to the management and detects the incipient faults in the system so that corrective actions can be initiated to avoid the major mishap, downtime, and safety-related attributes. The guidance given in this publication is divided into two sections, tests carried out before the electrical installation is energized and those carried out with the installation energized. The tests specified by the Regulation should be carried out in the following sequence:

Tests before the supply is connected.

1. Continuity of protective conductors including main and supplementary equipotential bonding.
2. Continuity of ring final circuit conductors. Insulation Resistance.
3. Polarity.
4. Earth electrode resistance.

Tests with the electrical supply connected.

1. Earth fault loop impedance.
2. Check of phase sequence.
3. Functional testing.
4. Verification of voltage drop and supply frequency.
5. IR thermal Inspection.

 Tests before the supply is connected.

1. Continuity of protective conductors including main and supplementary equipotential bonding.

Every protective conductor, including circuit protective conductors, the earthing conductor, and main and supplementary bonding conductors should be tested to verify that all bonding conductors are connected to the supply earth. Tests are made between the main earthing terminal (this may be the earth bar in the consumer unit where there is no distribution board present) and the ends of each bonding conductor. Two methods are used for this test;

1. Test Method 1:
2. a) Temporarily link the line conductor to the CPC in the Consumer Unit.
3. b) Test between the line and the CPC at each accessory point e.g. a ceiling rose, switch or socket outlet.
4. Test Method 2:

Using a long test lead, test between the earth bar in the consumer unit and the CPC at each accessory point.

2. Continuity of ring final circuit conductors

The purpose of this three-stage test is to verify that:

1. a) The line, neutral and protective conductors form a continuous path around the circuit.
2. b) The ring circuit is wired correctly and consists of one loop only i.e. there are no `bridges. The tests are carried out such that each conductor forms a continuous path around the loop. Any higher resistance tested will indicate that a spur exists within the ring.
3. Insulation resistance.

The purpose of the insulation resistance test is to confirm that when all loads have been disconnected, no current-carrying paths exist between L and N conductors or between live conductors and CPC, i.e. there is sufficient insulation between the conductors.

4. Polarity

The polarity test is carried out to verify;
a) That all single-pole switches in lighting circuits are connected to the line conductor.
b) That the Centre pins of an Edison Screw (ES) lamp holder are connected to the line conductor.

5. Earth resistance test

A three-point wiener test method is commonly used for earth resistance measurements.

Earth resistance higher than those recommended in the standards are unsafe and requires immediate action by the client to improve.

A high earth resistance increases the earth loop impedance and may result in protective devices not operating within the designed time to save a life. In the case of a phase-to-earth fault, the current does discharge to the earth but circulates within or close to the source thus becoming a hazard to humans, animals, or property. The standards stipulate that all metallic parts associated with electrical installation must be appropriately bonded and connected to the grounding system.

Check of phase sequence

Normally a multiphase supply is designed to have a red phase, yellow phase, and blue phase sequence reference to the IEC60364 standard. This test seeks to establish consistency of the phase sequence to avoid some motor rotation in the reverse direction relative to the designed direction of rotation. The test is very important during the test and commissioning of an industrial facility with a Motor Control Centre (MCC).

Functional Testing.

1. Circuit breaker test

Regulation 411.3.2 of the IEC 60364 states that protective devices shall automatically interrupt the supply to the line conductor of a circuit of equipment in the event of a fault of negligible impedance between the line and an exposed-conductive part or a protective conductor in the circuit or equipment within the disconnection time required by Regulation 411.3.2, 411.3.2.3 or 411.3.2.4. On a recent electrical safety audit for a facility where electrocution occurred, it was noted that the circuit breaker could not trip to disconnect the supply and save a life due to high earthing resistance of 115.4Ohms. Other tests for advanced switching switchgear are proposed including but not limited to over-voltage withstand test, dielectric test on auxiliary circuit and control circuit, measurement of resistance of the main circuit or contact resistance test, SF6 breaker gas leakage test, Injection tests and mechanical operation tests.

2. Earth leakage test

Recent investigations indicate that leakage currents are present in most electrical installations within the country. This has been caused by a lack of load balance on the multiphase power supply. A load-schedule helps the facility to maintain a certain load on specific consumer units (CU) or distribution boards (DB) as planned so as not to exceed design parameters.

According to Kirchhoff’s current law, high current will flow through the neutral conductor in the worst case of load imbalance on a transformer. This has resulted in diverted neutral currents dominant in the TNCS system (Where the functionality of earth and neutral are combined) which is the utility’s preferred mode of connection to a facility in Kenya. As much as the TNCS mode is more preferred in this country now does not mean it is suitable for all types of electrical installations. Electrical installations to hazardous areas must be installed on a TNS system (Separate Earth and Neutral) of earthing to suppress the existence of diverted neutral currents in the system. Diverted neutral currents may lead to a spark leading to a fire or explosion in a petroleum storage or vending station.
Residual current devices are proposed for these circuits to interrupt the circuit in case a fault occurs.

Earth loop impedance test.

The earth fault loop impedance is given by: Zs = Ze + (R1+R2) The value of Zs can be found by:
I. measuring the earth fault loop impedance Zs at the furthest point.
I. measuring the earth fault loop impedance Ze at the incoming supply and adding (R1+R2).
II. Taking the earth fault loop impedance Ze provided by the distributor and adding (R1+R2).
Earth loop Impedance tests the speed of operation of the breaker in case a fault involving phase to ground occurs.
The lower the resistance of the earth loop impedance path (Zs) the faster the current flow to the ground and thus the speed of operation of the moulded case circuit breaker (MCCBs), Miniature circuit breakers (MCBs) or Residual Current Circuit Breaker with over current protection (RCCBO).

Prospective fault currents (PFC) are measured also with this test to ensure that the switchgear can withstand the prospective currents flow. The total of external earth loop impedance Ze
(Utility earth fault loop impedance) and the internal earth loop impedance (R1 + R2) makes the system earth fault loop impedance Zs. Zs and prospective fault currents (PFC) must be estimated mathematically during design and proofed during periodic electrical safety audits to ensure effective speedy operation of the switchgear.

Verification of voltage drop and supply frequency:

Voltages test cross phases, phase to neutral, phase to earth, neutral to earth must be conducted with respective frequency levels recorded. IEC 60364/BS7671 requires that the maximum permitted levels of Voltage drop as referenced in BS7671 Table 4Ab (i) 3% for lighting (6.9V) or 5% for other uses (11.5V). These voltage-drop limits refer to normal steady-state operating conditions and do not apply at times of motor starting, simultaneous switching (by chance) of several loads, etc. as mentioned in Estimation of actual maximum kVA demand (diversity and utilization factors, etc.). When voltage drops exceed, the values shown in Figure 1. A larger cable cross-section area must be used to correct the condition.
The value of 8%, while permitted, can lead to problems for motor loads, for example:
In general, satisfactory motor performance requires a voltage within ± 5% of its rated nominal value in
steady-state operation. Starting current of a motor can be 5 to 7 times its full-load value (or even higher). If an 8% voltage drop occurs at full-load current, then a drop of 40% or more will occur during start-up. In such conditions the motor will either:

1. Stall (i.e. remain stationary due to insufficient torque to overcome the load torque) with consequent
   over-heating and eventual trip-out
2. Or accelerate very slowly, so that the heavy current loading (with possibly undesirable low-voltage effects on other equipment) will continue beyond the normal start-up period.

Finally, an 8% voltage drop represents a continuous power loss, which, for continuous loads will be a significant waste of (metered) energy. This might feature in energy audit as a high cost of electricity but difficult for nonelectrical personnel to find out the cause and prevention. For these reasons it is recommended that the maximum value of 8% in steady-state operating conditions should not be reached on circuits which are sensitive to under-voltage problems for Maximum voltage drop values for circuits other than lighting circuits.

IR thermal Inspection

Infrared (IR) technology has evolved into one of the most effective technologies for preventing failures and the added benefit of not requiring an outage to carry out, as it can be done on live cables and systems. Several further benefits of infrared technology are

(1). Hot spots such as loose connections and bad contacts.

(2). Under-rated cables overheating under existing
load demand.

(3) Loads Imbalance.

(4) Stressed earth leakage units, circuit breakers, conductors, and other electrical elements. International standards have set out rating for thermal inspection, a change in temperature (ΔT) with respect to the ambient temperature shall be used to classify the thermal anomaly into category 00, 01, 02, 03 and 04 to NETA standards.

With soaring numbers of electrocution, fire and explosion related to electrical installations, electrical safety audit point out the non-compliances of an electrical installation to the executives so that corrective actions can be initiated to avoid the major mishap, down time, and safety-related attributes. Some importance of electrical safety audits are;

1. To ensure compliance with the statutory regulations, codes & standards.
2. To ensure facility and employee safety.
3. To minimize plant downtime and reduce production losses due to accidents.
4. To avoid machine / plant deterioration due to defective electrical systems and
5. Increase economic service life (ESL) of the plant

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Risk of Electrocution and Preventation
The consequences of electrocution span from compensation, loss of life and technical assets and missing loved ones.

The Risk of Electrocution

Everybody is at risk of electrocution when your body directly or indirectly contacts electrically energized live parts with electrical currents spanning from a few milliamperes to a few Amperes. Electrical appliances that consume electrical power outlet pose great danger from muscle fibrillation to severe burns and fatal accidents when the contact with electrical power is maintained for an extended period in case the supply is not interrupted by appropriate switch gear to isolate the source.

Electrocution Prevention

Do’s and Don’ts electrical systems

Do’s

• Only use plugs that fit the outlet.
• Make sure that electrical connections are tight.
• Check that the wire insulation is in good condition.
• Keep machines and tools properly lubricated.
• Use extension cords only when necessary and only if they are rated high enough for the application.
• Use waterproof cords outside.
• Only use approved extension lamps.
• Leave at least 3 feet of workspace around electrical equipment for instant access.
• Keep your work area clean. Be especially
  careful with oily rags, paper, sawdust, or
  anything that could burn.
• Follow manufacturer’s instructions for all electrical equipment.
• Allow electrical repairs to be performed by skilled and duly licensed electricians.

Don’ts

• Don’t overload outlets or motors.
• Don’t let grease, dust, or dirt build up on machinery.
• Don’t place cords near heat or water.
• Don’t run cords along the floor where they can be damaged.
• Don’t touch anything electric with wet hands.
• Don’t put anything but an electric plug into an electric outlet.
• Don’t use temporary wiring in place of permanent wiring.

Additional Electrocution Preventive Measures

Ensuring sound earthing/grounding creates a low-resistance path from a tool to the earth dispersing to the general mass of earth unwanted electrical currents which may affect the property, human or livestock. When a short circuit or lightning discharge occurs, energy flows to the ground, protecting you from electrical shock, injury, or death. Poor grounding increases the touch potential thus a higher risk of injury or death. It is a secondary method of preventing electric shock. Grounded electrical systems are usually connected to a grounding/earthing rod or earth mesh that is placed 3 to 8 feet deep into the earth’s surface depending on the earth’s resistivity of the area. When a facility is grounded, it means permanently connecting to the earth through a ground connection of sufficiently low impedance and having sufficient ampacity that ground-fault current which may occur cannot build up to voltages dangerous to personnel, animal, or equipment. High earth resistance values increase the earth fault loop impedance slowing down the operation of circuit breakers to save a life.

This article first appeared in an engineering magazine.