Trinidad and Tobago Electrical Regulations

Trinidad and Tobago electric RegulationsThe Trinidad and Tobago Electricity committee (TTEC) is responsible for the distribution and transmission of electrical verve around the country. The electrical antecedent comes from cardinal main power place which atomic subject 18 Port of Spain (308MW station, Point Lisas (634MW) station and Penal (236MW) station. It is through this arrangement the agency provides electrical power to its customers and quantifys this vigor in order to get hold revenue. However the governance is everywherely one of the most vulnerable move of that comp eachs infrastructure, as they argon prone to damage in a numberless(prenominal) of different scenarios. These reasons have ca utilise power companies such as TTEC to lay tear both(prenominal) of the strict standards, which we leave behind now be examined in detail. Since this taradiddle is concerned with industrial outfit administrations, mainly common chord- human body AC potential e ntrust be addressed. The energy that they issue is only single or three figure with frequency of 60 hertz.TRANSMISSION SYSTEMSCharacteristic of SupplyTTEC supplies energy with the following decl atomic number 18d voltages and characteristicsSingle conformation, 2 fit outs, one hundred fifteen volts employ for facility with loads up to a maximum of 30 amperes (A).Single physical body, 3 wire, and cxv/230 volts for in lineive reasoning with loads up to a maximum of deuce hundred amperes (A).Three phase, 4 wire, 115/230 volts from a delta- affiliated source for inst wholeations with combined light up and power loads up to a maximum demand of 199KVA. electric potential of 230 across phase wires, 115 amongst one after a nonher of two phase wires and hide outed neutral, and cc volts mingled with this third phase wire and neutral. (This third 200V phase wire essential be positively identified with the trick blue air throughout the founding or by whatever means of recognition is required by the codes in force.Three phase, 4 wire, 230/400 volts from a star affiliated source for facility with combined liberation and power loads up to a maximum of 350KVA.One of the following senior highschool voltages depending on the maximum demand of the load, location of the installation and the voltage unattached at the location put over lavishly voltage publish3 phase3 wire6.6KV3 phase3 or 4 wire12KV3 phase3 wire33KV3 phase3 wire66KV3 phase3 wire132KV*Accordingly the accusation should be consulted before the consumer makes plans for an installation to be supplied at high voltage.Consumers requiring supplies with utilization voltages other than the Commissions standard voltages as discussed above from (a) to (e) volition be supplied at one of the commissions high voltages decl atomic number 18d in (e) and are required to provide their own transformers. The Electricity Supply rules make to a lower place Section 15 of the Electricity (Inspection) Act Chapter 54.72 provides for variation of 6 pct above or below the declared voltages.As a solution a few guide rail capers are to be followed1. The post of communicate moldiness(prenominal)iness be near the face of a mental synthesis and at the commissions distribution pole.2. When the sequester voltage supply is available, the superman of supply for an installation supplied at 115/230 or 230/400 volts, mustiness be at the Commissions distribution pole3. If a transformer must be installed to supply the 115/230 or 230/400 volt then the transformer has to be the extremum of supply.4. The point of supply for a consumers installation supplied which is at high voltage provide each be the consumers end points which is connects to the supporter get out or the terminal of the commissions disconnecting means.Provided that the consumer has consulted the commission to determine the location of the point of supply (the point at which TTEC supplies energy) for the new-fashion ed installation, the commission shall provide only one military divine military utility line to supply a structure. The service lines are either electrical theatre getors through which energy whitethorn be supplied or is intended to be a supplied by the commission. These music directors are runs from the distribution main or forthwith from the premises of the Commission. check over figure below.Fig. 1 Typical Overhead Service Line with Consumers penetration business line on Consumers buildingFigure typical overhead service line with consumers arrest line of work on private pole pose OF SERVICE LINEThe position of the weather- head or gland at the point of enthral must be dictated at a lower limit distance of 15cm away from the bash board and non in the direct path of water flow from rooftops and guttering.It must be tincture also that the Commission only provides one service line to supply a building.The customers point of entrance must non be fixed directly abo ve a building extension or dissolve roof.The minimum meridian to which the overhead service conductors are to be committed are 3.7 metres above the terminate grade level, or for a great height it is requirement to maintain it at a minimum height of 6.1 metres for clearance of the Commissions over head service line over roads. each industrial installation shall be competently controlled by a manually operable, physically and electrically separated integrated main switch or circle circle surf. This disconnecting means shall be readily accessible to authorized or qualified personnel, properly identified and sort of located near to the service conductors as realizable.Conductors and blood linesService Entrance Conductors are the portion of the installation amongst the point of entrance and the consumers main disconnecting device. This generally means it is the customer lineage to which T TEC connects to give supply from the service line. The service line is attached to the dispersal main.TTEC service connects only to a single consumers entrance cable at the point of supply to a building. The overhead line service conductors must be connected at a minimum height of 3.7 molaritys above finished grade level. For height that is greater it is necessary maintain a minimum height of 6.1 clips for clearance of the service line over roads. The entrance cables to the point of supply shall be in either rigid golden conduit treated against corrosion or other clear non-corrosive enclosures or shall be concentric or tamper-proof cable form the consumers terminals to the criterioning equipment and should preferably continue to the consumers main switch. If conduit is utilize, only standard conduit elbows and fittings to facilitate pulling of the cables should be allowed. An approve weather head is required at the consumers terminals at the point of supply and a minimum of 0.5 criterions of cable must be go away for partnership to the Commissions overh ead service line. Attachment to the commissions conductors shall be make a point no less than 0.3 meters form the weather head. The consumer must also provide and install terminating lugs for connecting to cables with conductor sizings larger than 95mm2. For immunity entrance cables, it is best-loved that for 115/230V and 230/400V installations, the Consumers terminals at the point of supply be located at a pole furnished and maintained by the consumer.Size of Conductors Conduits And CablesThe surface of an entrance cable for a building with two or to a greater extent metered installations supplied at 115/230 or 230/400 volts shall not be less than 16 sq. mm. This cable size is for copper conductors with rubber, polythene or P.V.C. insulation. other(a) authorise cables rump be utilize with equivalent afoot(predicate) carrying capacities.The size of every conductor shall be such that its certain military rank, is necessary, of grade factors appropriate to the type of cable s and the conditions of installation, is not less than the maximum sustained accepted which testament popularly flow through it. Also the size of the conductor shall be that the voltage drop from the consumers terminals to any point in the installation does not exceed 2.5% of the declared nominal voltage when the conductors are carrying the maximum live low their normal conditions of service.Single core cables armoured with steel wire shall not be used for carrying alternating currentMINIMUM creation BENDING RADIUSDuring installation, PVC ar mored cables should not be circle to a smaller radius than six propagation the overall diameter for cables having circular conductors and eight times for other armored cables. Every cable termination shall be accessible for inspection and shall be mechanically and electrically sound. The insulation tape or braid shall be removed no further than is necessary.PROTECTION OF CABLESConductors of cables shall be insulated with the correct clas s of insulation in accordance with the appropriate standard to withstand a voltage not less than the highest sustained voltage to which they are likely to be subjected. both insulation damaged by soldering otherwise shall be trail away and replaced by suitable insulation at least(prenominal) as thick effective as the original installation. Termination of cables should not be in locations where flammable and/or explosive dust, liquid, vapor or grease-gun is likely to be present. Otherwise the termination shall be enclosed in a flameproof fitting. For paper or varnished-cambric-insulated, coat-sheathed cable, a wiped metallic element limb or joint cuff, filled with insulating compound shall be provided.Laying of cables under kingdomCables under fuse must be 18 deep inhumed in red sand (sand bed) surrounded by concrete slabs then cover with red danger tape over the slabs. If the cable is passing under a roadway, the cable must be a concrete duct and must be inspected before bei ng buried.Positioning of transformer and switchgearAll service equipment which include transformers, panels, switch gear etc, must have a working space of 3 feet around them, they must be positioned where they are considerably accessible to the authority, in an upfront foremost position away from unglamourous travel, if it is pedestrian travel place billards around them to disallow people from crashing into them.MeteringMetering flowerpot be accomplished through socket type metering or three phase metering, the later being more expensive. menses slip0 200Single phase200Three phase wiring200-500Current transformer metering500High voltage meteringGenerally, a single meter is used to measures all electrical energy supplied at that single location. It records the number of units (kilowatt hours) of electricity you have used and is quite easy to read, and consumption records are simple to keep. The Trinidad and Tobago Electricity Commission uses the recorded electricity usage to ac curately calculate the consumer electrical bill. The three types of meter normally use are the digital, the Dial and the AMI meters. The service entrance cable is connected to the meter. If a rail-divider box is to be used first rail-splitter box then the meter .If no splitter box is used, then connect only to the meter. Splitter arrangements can also be used to split the load.In metering in that location are a few regulations that must be followed in connexion, positioning and reading. They are as followedFor an indoor-type meter, the consumer shall provide a meter-board for mounting the meter. This board shall be of an approved size, and shall be made from 19mm hard-wood stock, free from knots set plumb, and level and securely fastened for impregnable supportsIn order to make meters more accessible, the tops of the meters should not be greater than 1.8m or less than 1.5m above bedeck or finished grade level. A clear space of at least 0.9m in front of all meters must be avail able at all times.Meters should not be located over doorways, along stairways or directly under water pipes or drain pipes. They should also be mount free from shock, vibrations and mechanical injury.Meter sockets should be installed on an outer argue of the building. In a building elevated more than 2.4m above ground, the meter should be located on one of the supporting columns of the building.Meters for a multi-level building shall be grouped in one location on either the basement or ground cut down in an accessible location. Where there are greater than 6-metered installations, groups of at least 6 meters can be installed on the basement, ground floor, or an accessible upper floor.Outdoor socket-type meters shall be installed for single phase 115/230V installations up to a maximum of 200A meter sockets of the ring less type can be used, but must be provided with an approved means for sealing the cover.Outdoor socket-type meters shall be installed for three-phase 115/230V and 23 0/400V. foundations with loads up to 200A per phase. Whole current or self-contained socket-type meters shall meter such installationsFor 201-500A loads per phase, current transformers shall be used. The commission shall install a current transformer cabinet, meter-board and meter cabinet where necessary. The meter cabinet shall have a minimum depth of 25.4cm. Between the current transformer cabinet and the meter board, a 20mm conduit containing three (3) 1.5mm2 red, white and blue, and four (4) 2.5mm2 red, white, blue and black 600V insulated conductors must be provided by the consumer. The conductors should be a maximum 15m in length. Lengths of at least 0.9m must be provided outside(a) the two ends of the conduit to permit the external connections to the meter and current transformer.Three-phase, 115/230V and 230/400V installations requiring loads in excess of 500A per phase shall be supplied and metered at high voltage. The metering unit shall be installed on a Distribution Po le or in the consumers transformer substation subject to the conditions of the supply.Fig. 4 Typical facility Single Metered Low Voltage SupplyFigure Single meter high voltage supplyCIRCUIT BREAKERSA hitch breaker is a device for closing and interrupting a move between separable contacts under both normal and abnormal conditions, with natural selection establish on the type of application being either alternating current (ac) or direct current (dc). The established voltage rating of a circuit breaker is based on its clearance or space, between electrical circuits and between electrical components and the ground. circuit breaker voltage ratings fate the maximum electrical system voltage on which they can be applied. round breakers voltage must be equal to or greater than voltage of the electrical system on which they are used. travel breakers have two types of current ratings continuous current rating and fault current-interrupting capacity.Low voltage (less than 1000 VAC) ty pes are common in domestic, commercial-grade and industrial application, includeMCB (Miniature circumference surf)-rated current not more than 100 A. Trip characteristics normally not adjustable. Thermal or thermal-magnetic operation. breaker illustrated above are in this category.MCCB (Molded Case Circuit Breaker)-rated current up to 1000 A. Thermal or thermal-magnetic operation. Trip current may be adjustable in larger ratings.Low voltage power circuit breakers can be mounted in multi-tiers in LV switchboards or switchgear cabinets.Positioning of circuit breakerA circuit breaker in a wet location or outside a building must be enclosed in a weatherproof enclosure. This enclosure must be so equipped as to prevent moisture and water from entering and accumulating within the cabinet.Circuit breakers must be mounted so that there is at least 6.35mmm of airspace between the enclosure and the wall or the supporting surface, with elisions being metallic cabinets and cut-out boxes whi ch may be installed without the airspace on a concrete, masonry, tile or similar surface.All circuit breakers should be installed at least 2m above the floor or working platform.FuseA mix in is placed in an electrical current circuit so that when current flow exceeds the rating of the fuse it blows or blows out. The elements in the fuse melt, break the circuit and preventing other components of the circuit from being damaged by the over current. The size of the metal fuse element determines the rating. Once a fuse blows it must be replaced by a new one.Standards for the Use of Circuit ledgeman and FusesThe minimum sizes of main switches or circuit breakers permitted on consumers installation are as followsCharacteristic of supplyMinimum Current rating115 volts, 2 wire, 1phase30 amperes115/230 volts, 3 wire, 1 phase60 amperes115/230 volts, 4 wire, 3 phase60 amperes115/400 volts, 4 wire, 3 phase60 amperesTable circuit breaker sizesThe consumer shall furnish and install a high volt age circuit breaker at the primary disconnecting means for an installation with a maximum demand in excess of 800 KVA.In a building with more than one separately metered Consumers Installation a metal splitter box with a suitably sized Circuit Breaker for each Installation shall be installed between the Consumers Entrance Cable and the meter sockets by the Consumer/s or Landlord. Provision shall be mode on the splitter box for the Commission to apply its seals or locks. to each one Circuit Breaker In the splitter box shall be suitably identified with the Consumers Installation connected to it.Where there are seven or more separately metered Consumers Installations in a building, a main disconnecting means or Circuit Breaker shall be installed between the Consumers Entrance Cables and the group of Circuit Breakers In the splitter box by the Consumers or Landlord. Provision shall be made for the sealing or locking of this switch or breaker by the Commission.Consumer shall furnish and install a high voltage Circuit Breaker as the primary disconnecting means for an Installation with a maximum demand in excess of 800 KVA. The Consumer should conform with the Commissions Specification with respect to the rating and rupturing capacity of the Circuit Breaker. The limits of the Consumers protection circumstance shall be stipulated by the Commission to ensure discrimination with the protection of the Commissions system.It is recommended that the Consumer maintain an adequate supply of chuck up the sponge per centums for the normal maintenance of his circuit breaker and ancillary apparatus.The selection of the type of circuit breaker most suitable for protection of a DC installation depends mainly on the following criteriaThe current, which determines the rating of the equipmentThe rated voltage, which determines the number of poles in series necessary for breakingThe maximum short-circuit current at the point of installation, which determines the breaking capacityTh e type of network.It is recommended that the consumer maintain an adequate supply of spare parts for the normal maintenance of his circuit breaker and ancillary apparatusBRANCH CIRCUITRYA branch circuit is delineate as that part of an electric circuit extending beyond the last circuit breaker or fuse. The branch circuits start at the breaker box and extend to the electrical devices connected to the service. Branch circuits are the last part of the circuit supplying electrical devices. These circuits are classified in two different ways, concord to the type of loads they serve or according to their current-carrying capacity. laborsThe table below show the supplies required for motors with different power rating.Motor power rating /wattsSupply750 and below115/230, single phaseBetween 750 and 5.6K230, single or 3 phase5.6K and over230/400, 3 phaseFor single-phase motors rated between 3.75 Kilowatts and 5.6 Kilowatts it should be arranged for no load starting. Motors of over 5.6 kilow atts must be arranged for reduced voltage starting. The commission will be prepared to consider direct online starting of motors of these sizes where the supply to the consumers installation is at high voltage. Any apparatus having power rating larger than 2.5 KVA can be supplied at either 115/230, single phase. utensil greater than 2.5KVA up to and including 15 KVA in size can be supplied at 230 volts, single phase. Any rating larger than 15 KVA in size can only be supplied from a three-phase supply. Single-phase appliances and motors supplied from a 3 or 4 wire installations shall be so connected that the in operation(p) current unbalanced would be a minimum. Three phase motors should be protected against single phasing conditions. When the rotor of the motor is locked, the motor requires the highest current. Direct online starters can be used also, if current goes and comes.PlugsPlugs in most residential and commercial establishments do not exceed 150V between conductors on bra nch circuits. That is, they are normally rated at 15-20A with exception to a 240V circuits.LightingLighting circuits usually do not exceed 150 watts to ground. These circuits are usually rated at 15 amperes or less in most homes and commercial establishments callable to the fact that at some time during the use of the device the consumer may see the need to replace the fixture.Qualify personnel only should service the sacking fixtures. When installing for industrial purposes the voltage to the ground on the lighting circuit could be as much as 330V. With these conditions incandescent fixtures must be mounted 8 feet or more above the floor or at the available height. Where conditions do not permit 8 feet, then the fixtures should not be readily accessible (i.e. they should be encased, etc). much(prenominal) a supply would be provided by a 3-phase, 4-wire 277/480V wire system.For unrestricted and commercials areas the voltage should not exceed 300V to the ground. Trinidad and Toba go wiring code law states that no final circuit should provide more than 15 lighting fixtures.Type of receptacleMaximum Number of OutletsMaximum Branch Rating (Amps)Maximum Cable Cross-section (mm2)RemarksDOMESTICSocket outlet other than kitchen or laundry6202.515 A duplex houseKitchen2202.515 A DuplexLaundry1202.520 A DuplexAir condition1202.515 A, 230V DuplexINDUSTRIALLighting6 x 115V8 x 115V15201.52.5200VA per outletReceptable outlets3451520301.52.54.0500VA per outletGROUNDINGGrounding is one of the most burning(prenominal) factors involving electrical wiring, it provides safety to personnel, equipment and safety.Standards for Groundingi) All wiring installations shall include a consumers earth terminal or the equivalent to which the following shall be connected by an earth-continuity conductorAll metal work associated with the wiring system including cable sheets, armor, conduits, ducts, and boxes. open metal of apparatus land terminals of socket-outletsOne point of the second ary twisting and of the metal work of any transformer used in the installation, except where the transformer is contained in apparatusii) The connection to the earth electrode or any other means of hide shall be readily accessible and thoroughly made by use of soldered joints or substantial clamps of non-ferrous material and where connection is made to a metal pipe of external diameter not exceeding 100mm, clamps of an approval type shall be used.iii) The earthing lead shall be connected to the line side of the consumers main disconnecting means, to an effective earth electrode buried in the ground, for example a metal water pipe system having metal to metal joints or to a copper strip or rod. Connection to a water pipe shall be made as near as practicable to the point of entry onto the ground. Gas holler or non-metallic water piping shall not be used. Metal frames or portable, stationary and fixed electric appliances operating on circuits above 50 volts to ground shall be earth ed in an approved manner. Metal fixtures and lighting equipment installed on outlets wired with grounded multicore cable, with metal raceway, grounded metal-clad cable, non-metallic sheathed cable on circuits operating at more than 50 volts to ground shall be earthed.iv) Socket-outlets and cord connectors equipped with institution contacts shall have those contacts effectively earthed. The branch circuits or branch circuit wiring shall include or provide a instauration conductor to which the earthing contacts with the receptacle or cord connector shall be connected. The armour of the metal-clad cable or a metallic raceway is acceptable as a ground connector. Equipment shall be considered as grounded where mechanically connected in a ageless and effective manner to metal raceway, the armour of the meta-clad cable, the grounding conductor in a non-metallic or to a separate grounding conductor not smaller than 2.5mm2, provided that the raceway or grounding conductor is itself ground ed in an approved manner.v) The earthing arrangements of the consumer installation shall be such that on the occurrence of a fault of negligible impedance from a phase or non-earthed conductor to adjacent exposed metal, a current corresponding to 3 times the rating of the fuse, or one and a half times the setting of the over-load circuit-breaker can flow, so that the faulty circuit can be made dead. Alternatively and in every instance where this requirement cannot be met, an earth-leakage circuit breaker shall be installed. A voltage-operated earth-leakage circuit breaker shall be connected between the consumer earth terminal and a suitable earth electrode. The connection between the earth terminal operating coil and earth electrode shall be insulated.Grounding of buildings and equipmentIt is standard for all wiring installations to have an earth terminal or grounding electrode.The earth terminal must be connected in the appropriate manner to the circuitry of the installation by mea ns of the earth continuity conductor or the grounding electrode conductor.Where there is a transformer outside of the building there must also be an additional ground connection from the grounded service conductor to a grounding electrode, either at the transformer or elsewhere outside the building. A grounding connection must not be made however, at the load side of the service disconnecting means.Where an installation consists of multiple buildings, a grounding conductor must be made at each building.All the socket outlets and cord connectors in an installation equipped with grounding contacts must have them effectively earthed.The branch circuits or branch wiring must include a grounding conductor to which the earthing contacts shall be connected.As a standard all metal fixtures and lighting equipment installed on outlets wired with grounded multi-core cable, metal raceway, grounded multi-clad cable and non-metallic sheathed cable on circuits operating at more than 50 volts to gr ound must be earthed.In turn equipment are considered grounded if they are mechanically connected in a permanent and effective manner to a metal raceway (the armour of a metal-clad cable), the grounding conductor in a non-metallic sheath or to a separate grounding conductor not smaller than 2.5mm2, provided that the raceway is itself earthed in an appropriate manner.Switch plates, wiring boxes, conduit, cabinets, and lightsTypes of equipment that should be groundedAll metal work associated with the wiring system including cable sheets, armour, conduit, ducts and boxesExposed metal apparatusEarth terminals of socket-outletsOne point of the secondary winding and of the metal work of any transformer used in the installation with the exception of transformers contained in apparatus.Electric motor framesEquipment needs to be grounded under any of these circumstancesThe equipment is within 8 feet vertically and 5 feet horizontally of the floor or walking surface.The equipment is within 8 feet vertically and 5 feet horizontally of grounded metal objects you could touch.The equipment is located in a wet or smother area and is not isolated.The equipment is connected to a power supply by cord and plug and is not double-insulated.Types of earth electrodesEarth matsEarth mats typically resemble a wire mesh. They are used where there are high voltages, and several cables carrying those high voltages (such as in industrial areas). Each of the multiple cables is grounded to the earth mat rather than connecting all these cables to one grounding electrode. They are used mainly in substations and can be placed above or below ground. Earth plates are used to accomplish an effective earth in shallow soils with underlying rocks or in locations with large amounts of buried services. They can also provide protection at potentially dangerous places e.g. HV switching positions.Copper Earth RodsCopper rods of 20mm or 25mm diameter are used where there are high-resistance earth condit ions. It is possible to obtain copper rods with end-on connections where a length may be control in, the removable hard-steel tip unscrewed, and a further length of rod screwed on. Earth rods take advantage of lower resistivity soils at greater depths than normal excavation will allow. Quality earth rods are commonly made from either solid copper, stainless steel or copper bonded steel.http//tbn1.google.com/images?q=tbnIODNxco1mtW8xMhttp//www.rcoombs.co.uk/earthstake.jpg1 spunkMain types of lighting fixtures used in workshopsTubular Fluorescent LampsThe high efficiency and relative luminous intensity of such types of lamps results in their grand use in many workshops. However, fluorescent lamps are highly contrary for the lighting of areas containing moving or rotating machinery. The lamps can cause a strobe effect that makes it difficult to observe the movement of the machine and, in some cases, the machine may appear to be stationary.Color Corrected atomic number 80 LampsThese lamps, when used in conjunction with external reflectors are extensively used in industrial lighting, both inside the building and outside.Incandescent strand LampsThe small filament size allows close optical control for directive and local lighting.Glare Reduction-Glare occurs when a light source is seen directly, or by reflection, and is too bright when compared with the general brightness of the rest of the interior. The color of light used in a building should be elect so as to prevent excessive glare. There are two types of glare, viz. disability glare (which impairs vision) and discomfort glare (which causes visual discomfort). Lamps of liaise or warm colors should be used for general lighting in order to prevent or minimize glare.Reducing the brightness of the source causing the glare or changing the relative positions of the commentator and the source can also reduce glare. Lamps should be shielded from direct sight by louvers or reflectors. Also, diffusing ceilings ma y be used in order to spread the light over a wider are