ELECTRICAL INSTALLATION DESIGN

DET 207

• Define the IEC voltage standard and recommendations

• Define and explain TNB supply schemes

• Define and explain types of supply application

Chapter 1: Introduction Electrical Installation Design

IEC Voltage Standard and Recommendation

The International Electrotechnical Commission (IEC) is a not-for-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies.

IEC standards cover a vast range of technologies from power generation, transmission and distribution to home appliances and office equipment, semiconductors, fibre optics, batteries, solar energy, nanotechnology and marine energy.

Today, the IEC is the world's leading international organization in its field, and its standards are adopted as national standards by its members.

IEC standards have numbers in the range 60000–79999 and their titles take a form such as IEC 60038 : Voltage standard. The numbers of older IEC standards were converted in 1997 by adding 60000, for example IEC 27 became IEC 60027.

IEC Voltage Standard and Recommendation

International Standard IEC 60038 defines a set of standard voltages for use in low voltage and high voltage AC electricity supply systems.

IEC Voltage Standard and Recommendation

Definition of High Voltage :

The numerical definition of high voltage depends on the context of the discussion. Two factors considered in the classification of a "high voltage" are the possibility of causing a spark in air, and the danger of electric shock by contact or proximity. The definitions may refer either to the voltage between two conductors of a system, or between any conductor and ground.

In electric power transmission engineering, high voltage is usually considered any voltage over approximately 35,000 volts. This is a classification based on the design of apparatus and insulation.

IEC Voltage Standard and Recommendation

Definition of High Voltage :

In the United State 2005 National Electrical Code (NEC), high voltage is any voltage over 600 V .British Standard BS 7671:2008 defines high voltage as any voltage difference between conductors that is higher than 1000 V AC or 1500 V ripple-free DC, or any voltage difference between a conductor and Earth that is higher than 600 V AC or 900 V ripple-free DC.

The International Electrotechnical Commission defines high voltage circuits as those with more than 1000 V for alternating current and at least 1500 V for direct current.

IEC Voltage Standard and Recommendation

Definition of Low Voltage :

Low voltage is an electrical engineering term that broadly identifies safety considerations of an electricity supply system based on the voltage used.

"Low voltage" is characterised by carrying a substantial risk of electric shock, but only a minor risk of electric arcs through air.

The United States 2005 National Electrical Code (NEC) defines low voltage as any voltage under 600 V

British Standard BS 7671:2008 defines low voltage as • 50–1000 V AC or 120–1500 V ripple-free DC between conductors; • 50–600 V AC or 120–900 V ripple-free DC between conductors and Earth.

The International Electrotechnical Commission defines low voltage as any voltage in the range 50–1000 V AC or 120–1500 V DC

IEC Voltage Standard and Recommendation

Definition of Low Voltage :

Where two voltages are given below separated by “/”, the first is the root-mean-square voltage between a phase and the neutral connector, whereas the second is the corresponding root-mean-square voltage between two phases. The three-phase voltages are for use in either four-wire (with neutral) or three-wire (without neutral) systems.

Three-phase 50 Hz• 230 V / 400 V • 400 V / 690 V • 1000 V

Suppliers using 220 V / 380 V or 240 V / 415 V systems were expected by the standard to migrate to the recommended value of 230 V / 400 V by the year 2003. This migration has already been largely completed, as least within the European Union.

IEC Voltage Standard and Recommendation

Definition of Extra Low Voltage :

The International Electrotechnical Commission and its member organizations define an ELV circuit as one in which the electrical potential of any conductor against earth (ground) is not more than either 50 volts RMS (70 volts peak) for alternating current, or 120 volts for direct current.

TNB Supply Schemes

TNB customers are connected with power from hydroelectric and thermal plants through a network system made up of transmission lines, substations and distribution lines. Through this system, TNB supplies electricity to customers consistently and continuously by ensuring a balance between demand and supply at all times.

TNB Supply Schemes

TNB Supply Schemes

The basic concept behind hydroelectric power generation is the utilization of energy from flowing water as it descends from a height, where potential energy is converted to electrical energy. A hydroelectric power station requires a means of conveying water to produce the force necessary to spin a turbine linked to an electric generator, usually through a conduit such as a pipeline or tunnel to a turbine-generator which is spun by the passing water. TNB hydroelectric power stations are classified as either storage, run-of-river.

Hydroelectric Power Plants

There are 3 hydroelectric schemes with installed generating capacity of 1,911 MW with 21 dams in operation :

1. Sungai Perak hydroelectric scheme, with 1,249 MW installed capacity.2. Terengganu hydroelectric scheme, with 400 MW installed capacity 3. Cameron Highlands hydroelectric scheme, with 262 MW installed capacity.

TNB Supply Schemes

TNB’s thermal plants produce power using conventional steam turbine and steam generator principally fired by coal, oil or natural gas (steam power plant), gas-fired or diesel-fired open cycle gas turbine generators, and gas-fired or diesel-fired combined cycle turbine generators.

Thermal Power Plant

There are 6 major thermal power plants with installed generating capacity of 4,435 MW in operation, plus 3 thermal plants with 4,950 MW operated as IPP plants.