ELECTRICAL AND INSTRUMENTATION TECHNOLOGYCGE535 ELECTRICITY DISTRIBUTION AND SAFETY

POWER SYSTEM PROTECTIONTypical electrical power system consists of distribution lines, which are subjected to internal or external faults.

Since an uninterrupted electrical energy supply is a need in todays world, electric power system should ensure the availability of electrical energy at all times.

Switchgear is the device used to control supply of electric power and to protect the equipment in the event of abnormal condition, thus ensuring the continuous supply of electric power. It is the combination of electrical disconnect switches, fuses or circuit breakers.

POWER SYSTEM PROTECTION

The function of a protection system are:Isolate faulty equipment so that remainder of the system can continue to operate successfully.To limit damage of equipment.

POWER SYSTEM PROTECTION

TARIFFTariff means the schedule of rates framed for supply of electrical energy to the various categories of consumers. There are a few types of tariffs such asFlat Demand Tariff.This tariff is expressed as energy charges as the number of loads times the rate per load. Simple Tariff.This tariff is expressed as the energy charges per unit times the total electrical energy consumed in units or kwh. Flat Rate Tariff. The different types of consumers are charged at different rates i.e. the flat rate for light and fan loads is slightly higher than that for power load.

TARIFFStep Rate Tariff.The step rate tariff is a group of flat rate tariffs of decreasing unit charges for higher range of consumption.Block Rate Tariff.This type of tariff a given block of energy is charged at higher rate and succeeding blocks of energy are charged at progressively reduced rates.Hopkinson Demand Rate or Two Part Tariff.The total energy charge to be made to the consumer is split into two components namely fixed charge and runign charge.This type of tariff is expressed asMaximum Demand Tariff.This tariff is similar to that of two part tariff except that in this case maximum demand is actually measured by a maximum demand indicator instead of merely assessing it on the basis of rate able value.

TARIFFKVA Maximum Demand Tariff.A modified form of two part tariff.In tis case maximum demand is measured in Kva instead of in kw. This type of tariff encourages the consumers to operate their machines/equipment at improved power factor because low power factor will cause more demand charges.Doherty Rate or Three Part Tariff.In this tariff total energy charge is split into three elements namely fixed charge, semi-fixed charge and variable charge.Off Peak Tariff.The load on the power station usually has pronounced peak loads in the morning and early evening and a very low load during the night.

TARIFF AND POWER FACTORThe relationship between current and power in an AC circuit is expressed by the equation kW = kVA x Power Factor

The power factor is a number between 0 and 1. For a given power consumption, the current drawn is higher than necessary if the power factor is less than 1.

The power factor can affect the cost of electricity. Power factor only affects the maximum demand component of the network charges. Generally, kVA demand tariffs are structured to be revenue neutral compared with kW demand tariffs at a power factor of 0.8

SAFETYExtra low Voltage (ELV)ELV in electricity supply is one of several means to protect against electrical shock. An ELV circuit is defined by The International Electrotechnical Commission and its member organizations as one in which the electrical potential of any conductor against earth is not more than either 25 volts RMS (35 volts peak) for alternating current, or ripple-free 60 volts for direct current under dry conditions. Lower numbers apply in wet conditions, or when large contact areas are exposed to contact with the human body.The IEC defines three types of extra-low-voltage systems (FELV, PELV,and SELV), which are distinguished by their successively more restrictive safety properties

SAFETYIntrinsic safety (IS) is a protection technique for safe operation of electronic equipment in explosive atmospheres and under irregular operating conditions. The concept was developed for safe operation of process control instrumentation in hazardous areas, particularly North Sea gas platforms. As a discipline, it is an application of inherent safety in instrumentation.A device termed intrinsically safe is designed to not contain any components that produce sparks or which can hold enough energy to produce a spark of sufficient energy to cause an ignition.

SAFETYRegulationsElectricity Supply Act 1990 - Amended 2001An Act to provide for the regulation of the electricity supply industry, the supply of electricity at reasonable prices, the licensing of any electrical installation, the control of any electrical installation, plant and equipment with respect to matters relating to the safety of persons and the efficient use of electricity and for purposes connected therewith.Part V Section 23: Competent Control - Electrical plant or installation can be operated only by competent person holding the necessary qualifications/certificates or under supervision and charge of competent person. Failure to comply, fine max RM 10,000 and each additional day after conviction max RM 1000 if still fail to comply

SAFETYPart Vll Section 33: Notification of Accident or Fire Any accident/fire/damage to property to be reported immediately to EC and followed up by written report.EC shall direct authorised officer to investigate and report findings, with copy to magistrate if loss of life.If loss of life or serious injury, no alterations to plant until investigations are complete without permission of EC.If preliminary investigations show accident/fire was due to failure to comply with Act, or could have been prevented with proper precautions, EC will investigate further, and send a copy of the findings to the Prosecution if criminal negligence is found.Anyone concerned with the investigations may apply for a copy of the ECs investigation report.Part IX Section 37: Offences and PenaltyOffence - Tamper or adjust any installation or import or sell any equipment, which causes or likely to cause danger to human life or limb or damage to equipment/propertyPenalty - Fine < RM 100,000 or Jail < 5 years or both

SAFETYElectricity Regulations 1994Regulation 39: Treatment for Electric ShockInstructions in Bahasa Malaysia to be providedEmployer to confirm workmen know and understand the procedureRegulation 59: Suspension and CancellationCertificate of Competency can be suspended or cancelled by EC due to serious misbehaviorRegulation 63: Registration with ECAll holders of Certificate of Competency must register with ECRegulation 110: Inspection and Testing of InstallationInstallation to be inspected and tested by Competent PersonRegulation 111: Work on InstallationAll work on installation to be carried out by Competent Person or under his supervision

SAFETY

ReadingsEffectsSafe Current Values1 mA or less 1 mA to 8 mACauses no sensation - not felt. Sensation of shock, not painful; Individual can let go at will since muscular control is not lost.Unsafe current values8 mA to 15 mA 15 mA to 20 mA 50 mA to 100 mA 100 mA to 200 mA 200 mA and overPainful shock; individual can let go at will since muscular control is not lost. Painful shock; control of adjacent muscles lost; victim can not let go. Ventricular fibrillation - a heart condition that can result in death - is possible. Ventricular fibrillation occurs. Servere burns, severe muscular contractions - so severe that chest muscles clamp the heart and stop it for the duration of the shock. (This prevents ventricular fibrillation).