1.0 Purpose

The purpose of this standard is to define a set of mandatory requirements to ensure safety of personnel who work on or work with electrical equipment.

2.0 Scope

This standard applies to all HSC Sites. Strict adherence to the requirements of this Standard is mandatory.

3.0 Definitions

A competent person: is a person who possesses sufficient technical knowledge, experience and skills, through qualification or training i.e. he is an electrical engineer.

The competent person must be experienced in working on a specific electrical system or equipment and must be approved by the unit head to supervise the electrical jobs. He may be a company employee or a supervisor of a licensed electrical Sub-Contractor possessing the supervisory competency certificate.

“Voltage” means the difference of electric potential measured in volts, between any two conductors or between any part of either conductor and the earth as measured by a suitable voltmeter and is said to be:

“Extra Low”: A potential normally not exceeding 50 volts A.C., or 120 volts D.C. between conductors or between a conductor and earth. ii. “Low” where the voltage does not exceed 250 volts under normal conditions subject, however, to the percentage variation allowed under IE rules.

“Medium” where the voltage does not exceed 650 volts under normal conditions subject, however, to the percentage variation allowed under IE rules

“High” where the voltage does not exceed 33,000 volts under normal conditions subject, however, to the percentage variation allowed IE rules.

“Extra High” where the voltage exceeds 33,000 volts under normal conditions subject, however, to the percentage variation allowed under IE rule.

4.0 Regulatory compliance

Unit shall receive, maintain and review, whenever due for renewal, all statutory approvals like approval for connected load, electrical installation drawings and installation, NOC from State Electricity Board and electrical inspector for DG Sets as and when any change is made. Regular annual electrical inspection report by electrical inspectors if carried out must be available with the unit. All electrical equipment and appliances shall conform to applicable BIS standards / IE rules.

5.0 Electrical equipment - inventory, checking and testing

The unit shall establish and maintain a department wise combined inventory and testing schedule for all fixed electrical installations and portable electrical equipment / tools. All requirements stipulated in the testing schedule shall be rigorously followed. A formal visual inspection prior to undertaking a job shall be carried out by all personnel working in electrical systems / equipment.

Units shall maintain an up to date single line diagram for all electrical distribution systems. Electronic Equipment/Instrumentation items are also required to be handled by qualified and trained personnel. These persons should be trained on safety aspects.

6.0 Training and competence

The electrical technicians shall be trained to carry out formal visual inspection of each type of electrical equipment by the competent person(s). All personnel working on / with electrical equipment shall be retrained once every year or whenever there is a major change introduced in the electrical systems / equipment at the unit, whichever is earlier. The unit will document these training interventions by way of a comprehensive and specific record.

7.0 Earthing

7.1 Protection by providing earth conductors for all electrical apparatus and appliances is the PRIMARY requirement. This shall be provided for all existing and new installations as stipulated below:

All three-phase, medium and high voltage (>250 volts) equipment, all low voltage (<250 volts) movable equipment, portable electrical tools & appliances (except portable hand lamps of 50 volts and below) including their frames and metallic parts, and all plug sockets (low and medium voltage) shall be earthed by two separate and distinct connections with earth (double earthing).

All two-phase (also referred to as “single phase”), low voltage (<250 volts) equipment and their frames, including equipment considered generally inaccessible, shall be earthed by using a minimum of one connection with earth through a conductor.

All plug sockets shall be three-pin type, and the third pin shall be permanently and efficiently earthed. All sockets which are not three-pin type must be phased out, and in the interim, shall be provided with a separate conductor connected to earth.

The effectiveness of earthing through exposed and extraneous conductive parts for all electrical systems must be verified by measuring their resistance to earth. Resistance of individual earth pit system must be measured and ensured to be < 2 ohms at all times, and records maintained. Resistance of earth grid system shall be maintained at or below 1 ohm.

All earthing conductors shall be checked for connection up to the earth grid once in twelve months and findings recorded.

The earthing shall be carried out using properly sized conductors and shall be visible for inspection.

All earthing pits should have free access for maintenance.

Buildings and structures shall be protected against lightning as per IS 2309–1989.

During lightning, everyone working in open areas must be advised to come under shades which are protected by lightning arrestors.

7.2 Secondary Protection through Residual Current Circuit Breakers (RCCBs) & Earth Leakage Circuit Breakers (ELCBs):

RCCBs / ELCBs of adequate current rating shall be provided for:

All socket outlets in plants and office buildings including 3 phase socket outlets (e.g., welding socket outlet)

Movable/portable, electrical/electro-mechanical equipment e.g. welding machines, movable plant & equipment etc.

Air circulators and temporary construction power and lighting power distribution board.

7.3 Testing the RCCB: RCCB should be tested once in six months.

Failed RCCBs shall be replaced promptly. In the event the RCCB cannot be replaced immediately, the said connection should be isolated immediately & made inoperative. Similarly, in the event of the RCCB’s failing at the time of periodic audits, root cause would need to be ascertained as the period between failure & detection of failure of RCCB is a risky proposition & should clearly deal with any emergent environmental reasons for premature failures.

8.0 Working on or in the vicinity of live conductors

The risk associated with working on live conductors is extremely high. As a rule, no work shall be done on live conductors.

Only in extremely rare and unavoidable circumstances may 'live-working' be justified, these being limited to situations where the risk resulting from electrical isolation is greater than the risk from working on the live conductor (e.g. where the isolation would result in the shutdown of a critical safety system(s). Such situations should be covered by PTW to be authorized by the Maintenance Head only. For trouble shooting on individual circuits, it may be necessary from time to time to work on control circuits which are “live”.

PCC / MCC panels / equipment panels with 240V control circuits create a comprehensive program for identifying these locations and winding the transformer to favor 110V control circuits. Such control supplies shall be protected by an ELCB of 30 mA sensitivity. The decision to work on or near any live conductor must not be made on the basis of business exigency or on economic grounds.

9.0 Modifications to Electrical Systems or Equipment:

In general, electrical systems or equipment shall not be tampered with (including PCCs / MCCs / transformers etc.) and no unauthorized connections shall be permitted.

No modifications shall be carried out on fixed electrical installations or portable electrical tools without a “modification note” prepared and authorized both by a competent person and the maintenance head.

Modification note, when used, shall clearly identify the potential risks arising from the proposed modification and the actions to be implemented to mitigate all identified risks.

A separate modification note shall be prepared and authorized for each of the proposed modifications for equipment or a group of equipment.

Before energization of any new panel or after undertaking any major modifications to the electrical switchgear, it is being mandated that pre-commissioning checks be completed & formal records maintained.

It is recommended that for any major panel modification at site, the jobs should be done by the original manufacturer. Where it is logistically not possible for the panel to be modified by the original manufacturer, it should be carried out by approved agencies. In all such cases, the following procedure will apply:

Specific drawing approval by competent person (with specialist consultation, wherever necessary) before undertaking the modification

Carry out formal inspection of the modified panel at the works of the agency undertaking the modifications, prior to dispatch of the panel to site.

A relay coordination study would need to be carried & records maintained by all units

All electrical near misses / flashovers / burns to be reported.

10.0 Safety Systems of Work

A permit to work system, work method statement and a formal authorization to start/undertake/finish work (e.g. Permit/Licence to Work) must be obtained from a “Competent Person” before any work is undertaken on the following types of electrical equipment:

Live Conductors excluding testing on equipment panel control circuit

Main incomer switches and/or switchboards

Equipment having two or more sources of supply

Cables and other equipment on the supply side of a main incomer switch

Generating sets started by manual initiation from a remote location, or automatically on receipt of a remote signal

High-capacity rated uninterruptible power supply system

Description of work in PTW should be specific & clear. It is proposed to introduce PPE by way of protective suits for any work in panel / MCC rooms.

Electrician and Electrical Executives shall use insulated hand gloves and insulated safety shoes.

Use safety harness for working at a height of 6 Feet or above.

Insulated mats shall be placed in front and rear of main switchboard or any other control switchboard of medium voltage and above.

Standard first aid boxes containing materials should be provided in easily accessible locations and shall be periodically inspected to ensure that they are `fit and ready for use’ at all times of need.

All temporary cables should be removed as soon as the work is over.

All cables for project construction power should be laid only overhead with robust supports and not on the ground.

Rotary moving parts of all electrical equipment shall have guards to adequately cover all nip points.

Use multimeters (or series test lamps with fuse and two different colored wires) with short metallic lead for checking voltage and inspect the wires before every use.

All measuring / test equipment like multimeters, tong testers etc. should be checked periodically and log maintained. All worn out parts like test leads and clamps should be replaced by genuine spares only.

Ladders, when used, shall be insulated from earth.

“Danger Boards” should be permanently displayed on feeders where work is in progress.

Fuse pullers should be used while pulling out or replacing fuses, as it is very dangerous to use pliers for this purpose. Fuse pullers should be of the switchgear manufacturer’s make e.g. Siemens etc. and are easily available.

12.0 Systems for Equipment Isolation

The unit shall define the method of electrical isolation for access to every potentially dangerous moving machinery and / or equipment for the purpose of its operation, servicing and/or maintenance. This shall include either one of the following two alternatives namely a) removal of fuses or b) ‘lock out and tag out’ system, for secure & effective energy isolation / de-energization of the system (electrical pneumatic/ hydraulic) until such work has been completed and the normal safeguards e.g. guarding, can be fully restored. Test energization shall be carried out only by the competent person after ensuring that there is no danger to him or other personnel in the vicinity of the equipment.

13.0 Electrical Maintenance:

Unit shall prepare and follow electrical maintenance schedule and carry out maintenance as per site specific maintenance checklist.

Transformer oil break down value shall be checked once in a year. Protective relays shall be checked and calibrated once in a year.

14.0 Access to Electrical Substations, Transformers, Switch Rooms and Similar Areas

Access to electrical substations, transformers, switch rooms and similar areas containing high and low voltage equipment (e.g. main intake and distribution switchgear, motor control centers and similar) must be restricted to a limited number of designated competent persons.

Access to such areas must be physically secured to prevent unauthorized access e.g. doors/gates padlocked, and suitable prominent warning signs and information displayed.

The key components of an electrical system (e.g. busbar systems, switchgear and control gear, transformers, distribution boards and conductors) must all be clearly, legibly and durably marked with information plates and site equipment reference labels.

The operational state of electrical switchgear and control gear must be clearly shown by indicators, except when the main contacts can clearly be viewed.

15.0 Records

Earth Pit test records.

ELCB test records.

Transformer oil test records.

PTW.

LOTO register.

Relay test records