Equipment and Human Safety in Construction and Operation of Rural Electrification Network as per Electricity Regulation Nepal

Electricity Regulation, Nepal

The Electricity Regulation, 2050 has set some standards for the operation and maintenance of the transmission and distribution system. The standards set by the regulation are listed below.

SupplyVoltage: ­

1. The standard of supply voltage shall be maintained as follows:­
   1. 230Vin singlephaseand400Vin three phase for general consumers.
   2. For the consumers who want a supply of electricity from four wires, a service shall be made available in 230/400Vfrom three-phase AC system.

2. The tolerable limit of fluctuation allowed is ±5%.

High VoltageDistributionSystem: ­

1. The standard of the voltage in the high voltage distribution system shall be maintained as follows:­
   1. 3,300V
   2. 6,600V
   3. 11,000V
   4. 22,000V
   5. 33,000V

2. The tolerable limit of fluctuation allowed is ±5%.

High Voltage TransmissionSystem:­

1. The standard of the voltage in the high voltage transmission system shall be maintained as follow:­
   1. 33,300V
   2. 63,000V
   3. 132,000V
   4. 220,000V
   5. 400,000V

2. The tolerable limit of fluctuation allowed is ±10%.

Frequency:

1. The standard of the frequency shall be maintained as 50Hertz.
2. The tolerable limit of fluctuation allowed is ±2.5%.

Power Factor:

The standard of the power factor shall have to be maintained as follows:

1. The level of the power factor of the electricity supplied to the consumer should not beless than 0.8lagging and morethan oneunitleading.
2. Condensers or any other appropriate power factor improvement equipment shall be managed for maintaining the standard of power factor in electric transmissions and distribution system.
3. The consumer may have to install an appropriate condenser or a power factor improvement equipment the consumer's electricity related power factor is not within the level mentioned in the first statement.

Units of Measurement: ­

The following units of measurement shall be used for measuring different standard of electricity.

1. Milliampere, ampereor kiloamperefor themeasurementof electriccurrent
2. Millivolt, voltor kilovoltfor themeasurementoff voltage
3. Ohm, kiloohm, megaohm for themeasurementof resistance
4. Henry, millihenry or kilohenry for themeasurementof inductance
5. Microfarad, millifarador faradfor themeasurementof capacitance
6. Watt,kilowattor megawattfor themeasurementof active power
7. Kilowatt hour, megawatt hour for gigawatt hour for themeasurementof energy
8. VA, KVA or MVA for themeasurementof complex power
9. VAR, KVAR or MVAR for themeasurementof reactivepower

Minimum Clearances

1. The minimum clearance to be maintained from the conductor to the ground is given in the table below.

Note: In the case of voltage level more than 33 KV, 0.305 m should be added to the clearance for 33 KV for every 33 KV rise in voltage.

1. The minimum clearance to be maintained between a conductor and a house or a tree is given in the table below.

Note: In the case of voltage level more than 33 KV, 0.305 m should be added to the clearance for 33 KV for every 33 KV rise in voltage.

Some other points to be remembered

1. Electricity lines should not be drawn over houses nut lines of 400/230 V can be laid above a garage or a wall. The minimum clearance between the cable and the topmost structure should not be less than 3 m in this case.
2. Double insulators should be used for road crossings in dense areas for the voltage level of 11 KV and above.
3. If the same pole is to be used for cables at different voltage levels, the cables at higher voltage should be laid at the upper part of the pole.
4. All supports made of metals for high voltage transmission system should be grounded with a suitable earth wire. The stay wires used in the transmission and distribution system should have insulators at minimum 3 meters from ground level. In addition to that, the equipment used by the consumers such as air conditioners, heaters, etc. should also be earthed properly.
5. Changeover switches should be installed by the consumers who have installed generators for a backup supply.
6. Circuit breakers should be installed along with energy meters at consumer's premises. Consumers should also install an isolating switch near the energy meter.
7. Construction of any infrastructures near the transmission and distribution line is prohibited.
8. The supply should be given from a pole only and insulated wires/ cables should be used for this purpose.
9. The insulation resistance for 230/400 V system should not be less than 5 MOhm and 20 MOhm for 3.3 KV system. In case the voltage level is higher than 3.3 KV, an additional insulation resistance of 20MOhm should be added for each 1 KV rise in voltage.
10. Qualitative equipment should be used in the transmission and distribution system. The repaired equipment should be thoroughly tested and should conform to all the requirements before putting into operation.
11. Fuses and circuit breakers should be installed in the system to protect the system from dangerous effects of over current and short circuit current. Switches should be installed in the live wire but not the neutral wire in single phase systems.
12. Clearly visible warning signs and notice boards should be put up near the potentially dangerous zones. If it is not possible to put up the signs at all the places, it is absolutely necessary to put a notice board near the point of entrance.
13. Cutting the electricity supply for the purpose of repair and maintenance of electrical equipment and transmission and distribution systems is permitted with prior notice to the consumers. However, this may result in economic loss to the utility. The repair and maintenance work can be done on a live line if it is safe from the technical point of view.
14. Before carrying the repair and maintenance works on equipment, it is necessary to ensure that proper earthing has been done so that the equipment is completely dead.
15. The workers should be provided with all the necessary protective equipment for conducting repair and maintenance works. Insulated gloves should be used by the workers while working on live lines. Safety belts and shoes having rubber soles should also be provided for strong grip and protection against shocks is the worker is to work on high transmission towers.
16. In addition to the safety equipment, the workers should be provided with adequate training about the repair and maintenance works. They should also be provided with basic training regarding treatments to electric shocks. The actions to be taken for primary treatment, in this case, should be written clearly in Nepali and should be displayed to the workers.
17. First aid kit and basic treatment equipment should also be provided with basic training on how to use them. An electricity inspector should be appointed and informed about any accident in the organization. The inspector's duty is to inspect and instruct the workers for taking necessary safety measures to avoid accidents as much as possible.
18. In the case of an accident, the victim should be provided with primary treatment and should be taken to the nearest medical center as soon as possible. The nature of the accident should also be reported which gives a detailed about the person killed or injured (if an animal is killed, it should also be mentioned), time and date, place of the accident, electricity supply voltage and system, etc.

References

1. Nepal Electricity Authority. (2050 BS). Electricity Regulation 2050.Retrieved fromhttp://www.nea.org.np/

Information from class notes and handouts provided by my lecturer Mr. Gopal Joshi Subedi were also used.