Indian Standard Code-Abstract (IS:5613/IS:5039/IS:11892/IS:1455/IS:11171
Abstract of IS : 5613 for HV Line | |
Overhead Line | Pole Foundation hole should be drilled in the ground with the use of earth-augers. However, if earth-augers are not available a dog pit of the size I.2 x O.6 m should be made in the direction of the line. The depth of the pit shall be in accordance-with the length of the pole to be planted in the ground as given in respective Indian Standards. |
Tublar Pole | Steel Tubular Poles, Rolled Steel Joists and Rails – A suitable pad of cement concrete, stone or steel shall be provided at the bottom of the pit, before the metallic pole is erected. Where metal works are likely to get corroded ( points where the pole emerges out of the ground ), a cement concrete muff, 20 cm above and 20 cm below the ground with sloping top shall be provided. |
RCC Pole | RCC poles generally have larger cross-section than the PCC poles and, therefore, the base plates or muffing are usually not provided for these types of poles. However, for PCC poles, a base plate ( 40 x 40 x 7 cm concrete block ) shall be provided. Cement concrete muff with sloping top may also be provided, 20 cm above and 20 cm below-the ground level, when the ground or local conditions call for the same. |
H.V Line (120m To 160m Span) | The insulators should be attached to the poles directly with the help of ‘D’ type or other suitable clamps in case of vertical configuration of conductors or be attached to the cross arms with the help of pins in case of horizontal configuration. |
H.V Line (120m To 160m Span) | Pin insulator and recommended for use on straight runs and up to maximum of 10’ deviation. |
H.V Line (120m To 160m Span) | The disc insulators are intended for use a pole positions having more than 30’ angle or for dead ending of I1 kV lines. |
H.V Line (120m To 160m Span) | For lines having=A bend of 10” to 30’, either double cross arms or disc insulators should be used for HT lines up to 11 kV. For low and medium voltage line, shackle insulators should be used |
H.V Line (120m To 160m Span) | For Vertical configuration for Conductor erection: Distance between Pole’s Top to Disc insulation=200mm. Between Disc insulator to Disc Insulator=1000mm. Between Disc insulator to Guy Wire=500mm. |
Stay Wire Angle with Pole | Overhead lines supports at angles and terminal positions should be well stayed with stay wire, rod, etc. The angle between the pole and the wire should be about 45” and in no case should be less than 30”. If the site conditions are such that an angle or more than 30“ between the pole and the stay wire cannot be obtained, special stays such as, foot stay, flying stay or struts may be used |
Stay Wire | Hard drawn galvanized steel wires should be used as stay wires. The tensile strength of these wires shall not be less than 70 kgf/mm2. Only standard wires should be used for staying purpose. |
Stay Rod | Mild steel rods should be used for stay rods. The tensile strength of these rods shall not be less than 42 kgf/mm2 |
Stay Anchor | Stays should be anchored either by providing base plates of suitable dimensions or by providing angle iron or rail anchors of suitable dimensions and lengths. |
Guy Insulator | Stay wires and rods should be connected to the pole with a porcelain guy insulator. Wooden insulators should not be used. Suitable clamps should be used to coMeCt stay wires and rods to its anchor. For low and -medium voltage lines a porcelain guy insulator should be inserted in the stay wire at a height of 3 m vertically above the ground level. For high voltage lines, however, the stays may be directly anchored. |
Stay Setting | The inclination of stay relative to the ground is roughly determined before making the hole for excavation. This enables the position of the stay hole to be fixed so -that when the stay is set, the stay rod will have the correct inclination and will come out of the ground at the correct distance from the pole. The stay rods should be securely fixed to the ground by means of a suitable anchor |
O/H Conductor Drum | In loading, transportation and unloading conductor drums should be protected against injury. The conductor drums should never be dropped and may be Tolled only as indicated by the arrow on the drum side. The drums should be distributed along the route at distance approximately equal to the length of the conductor wound on the drum. |
Binding of O/H Conductor | The insulators should be bound with the line conductors with the help of copper binding wire in case of copper conductors, galvanized iron binding wire for galvanized iron conductors and aluminum binding wire or tape for aluminum and steelinforced aluminum conductors ( ACSR ). The size of the binding wire shall not be ‘less than 2 mm” |
Different Voltage on Same Support | Where conductors forming parts of systems at different voltages are erected on the same supports. Adequate clearance and guarding shall be provided to guard against the danger to lineman and others from the lower voltage system being charged above its normal working voltage by leakage from or contact with the higher voltage system. The clearance between the bottom most conductor of the system placed at the top and the top most conductor of the other system should not be less than 1.2m. |
Jumper | Jumpers from dead end points on one side of the pole to the dead end side on the other wide of the pole should be made with conductor of same material and current carrying capacity as that of the line conductor. The jumpers should be tied with the line conductor with a suitable clamp. If the material of the jumper wire is different from that of the line conductor, suitable bimetallic clamps should be used. If copper and aluminium bimetallic clamps are to be used, it should be ensured that the aluminium conductor is situated above the copper conductor so that no copper contaminated water comes in contact with aluminium. |
Jumper Clearance | For high voltage lines the jumpers should be so arranged that there is minimum clearance of O.3 m under maximum deflection condition due to wind between the live jumpers and other metallic parts. This may involve erection of insulators and dead weights specially for fixing the jumpers. |
Binding of O/H Line | Length of Binding wire on Insulator (From outer surface if Insulator to end of binding wire) should be 6D(Where D=Diameter of O/H Conductor) |
O/H Patrolling | All overhead lines should be patrolled periodically at intervals not exceeding 3 months from the ground when the line is live. |
Pole Earthing | All metal poles including reinforced cement concrete and pre-stressed cement concrete poles shall be permanently and efficiently earthed. For this purpose a continuous earth wire shall be provided and securely fastened to each pole and connected with earth ordinarily at 3 points in every kilometre, the spacing between the points being as nearly equidistant as possible. Alternatively each pole, and metallic fitting attached thereto shall be efficiently earthed. |
Stay wire Earthing | All stay wires of low and medium voltage lines other than those which are connected with earth by means of a continuous earth wire shall have an insulator inserted at a height of not less than 3 m from the ground. |
Earthing Wire Size | The cross-sectional area of the earth conductor Sims not be less than 16 mm2 if of copper, and 25 mm2 if of galvanized iron or steel. |
Conductor Clearance | Fixing Cross Arm in Low and Medium Voltage in Horizontal Configuration: |
P-P-N Clearance | Up to 650V Horizontal “V” Shape Cross arm(P-P(Street Light)-Neutral): Phase to Neutral=750mm , Phase to Phase(Streetlight at Top of Pole)=325mm,Last Phase-Cross Arm end=80mm |
P-P-N Clearance | 650V to 11KV Horizontal Cross arm(P-P(Street Light)-N) : Phase-Phase=300mm,Phase-Phase(Street Ltg)=300mm, Phase-Neutral=300mm,Last Phase-Cross Arm end=80mm |
P-P-N Clearance | Low and Medium Voltage Line (Horizontal Configuration): Less than 75cm Sag =P-P 30cm 76cm To 120cm Sag =P-P 45cm 121cm To 145cm Sag =P-P 60cm |
P-P-N Clearance | Low and Medium Voltage Line (Vertical Configuration): Less than 70m Sag =P-P 20cm 71m To 100m Sag =P-P 30cm |
P-P-N Clearance | High Voltage Line (Horizontal Configuration): Up to 120m Sag =Phase to Phase= 40cm 140m To 225m Sag =Phase to Phase= 65cm |
P-P-N Clearance | Double Circuit on Same Pole at different level : Distance between Two Circuit is 120cm. |
O/H Conductor | Choice of Conductors: The physical and electrical properties of different conductors shall be in accordance with relevant Indian Standards. All conductors shall have a breaking strength of not less than 350 kg. However, for low voltage lines with spans less than 15 m and installed either on owner’s or consumer’s premises, conductors with breaking strength of not less than 140 kg may be used. |
Voltage Variation | In accordance with the Indian Electricity Rules voltage variation for low voltage lines should not be more than ± 6 percent and for high voltage lines should not be more than ± 6 percent to ± 9 percent |
Span (Up to 11KV) | Recommended Span Lengths: The recommended span lengths for lines up to 11 kV are 45, 60, 65, 75, 90, 105 and 120 meters |
Span (Up to 11KV) | There are no fixed rules for spacing arrangement of overhead line conductors. However, the following formula gives an economical spacing of conductors: D=500+18U+(L*L/50) Where D=Spacing between conductor(mm), U=Voltage(p-p in kv),L=Span in meter |
Clearance(Up to 11KV) | Min height of any conductor of an overhead line across any street (Low Medium Voltage)=5.8m |
Clearance(Up to 11KV) | Min height of any conductor of an overhead line across any street (High Voltage)=6.1m |
Clearance(Up to 11KV) | Minimum height of any conductor of an overhead line along any street(Low &Medium Voltage)=5.5m |
Clearance(Up to 11KV) | Minimum height of any conductor of an overhead line along any street(High Voltage)=5.8m |
Clearance(Up to 11KV) | Minimum height of any conductor (bare) of an overhead line erected elsewhere(Low &Medium Voltage)=4.6m |
Clearance(Up to 11KV) | Minimum height of any conductor (bare) of an overhead line erected elsewhere(High Voltage)=4.6m |
Clearance(Up to 11KV) | Minimum height of any conductor (insulated) of an overhead line erected elsewhere(Low &Medium Voltage)=4.0m |
Clearance(Up to 11KV) | Minimum height of any conductor (insulated) of an overhead line erected elsewhere(High Voltage)=4.0m |
Clearance(Up to 11KV) | Minimum clearance of overhead line conductor from buildings(Low & Medium Voltage)=2.5m |
Clearance(Up to 11KV) | Minimum clearance of overhead line conductor from buildings(High Voltage)=3.7m |
Span(11KV To 220KV) | System Voltage Number Of Circuit Span (Meter) 33KV (over Pole) Single 90 To 135 Meter 33KV Single 180 To 305 Meter 33KV Double 180 To 305 Meter 66KV Single 204 To 305 Meter 66KV Double 240 To 320 Meter 220KV Single 320 To 380 Meter 220KV Double 320 To 380 Meter |
Danger Plate(11KV To 220KV) | Danger and number plates are located on Face (Feeding End (S/S))of pole |
Anti Climbing Device(11KV To 220KV) | Leg 1 (Right End Leg (Feeding End (S/S)) represents the leg with step bolts and anti-climb device gate if any. If two legs with step bolts are required, the next is No. 3 leg (Dignotical opposite of Leg1) |
Clearance(11KV To 220KV) | Voltage Circuit P-P Vertical P-P Horizontal 33KV (over Pole) Single 1.5 Meter 1.5 Meter 33KV Single/Double 1.5 Meter 1.5 Meter 66KV Single/Double 2.0 Meter 3.5 Meter 110KV Single/Double 3.2 Meter 5.5 Meter 220KV Single/Double 4.9 Meter 8.4 Meter |
Clearance(11KV To 220KV) | In case triangular formation has to be adopted, the conductor lying below an upper one shall be staggered out by a distance of X=V/150 Where V=System Voltage, X=staggered distance in meters |
Clearance(11KV To 220KV) | The earth wire sag shall be not more than 90 percent of the corresponding sag of power conductor under still air conditions for the entire specified temperature range |
Clearance(11KV To 220KV) | Line Voltage(KV) Spacing between P-E (m) 33KV 1.5meter 66KV 3.0meter 110KV 4.5meter 132KV 6.1meter 220KV 8.5meter |
Earthing(11KV To 220KV) | All metal supports and all reinforced and prestressed cement concrete supports of overhead lines and metallic fittings attached thereto, shall be permanently and efficiently earthed. For this purpose a continuous earth wire shall be provided and securely fastened to each pole and connected with earth ordinarily at 3 points in every kilometer, the spacing between the points being as nearly equidistant as possible. Alternatively, each support and metallic fittings attached thereto shall be efficiently earthed. |
Earthing(11KV To 220KV) | Each stay-wire shall be similarly earthed unless an insulator has been placed in it at a height not less than 3.0 meters from the ground |
Tower Height (up to 400KV) | The transmission lines and transmission line structures of height 45 m and above shall be notified to the Directorate of Flight Safety (DFS), Air Headquarters (Air HQ), New Delhi. |
Tower Height (up to 400KV) | For construction of any transmission line/structure or a portion thereof, falling within a radius of 20 km around the Defence aerodromes and air to firing ranges provisions of the Aircraft Act 1934, Section 9A as amplified by the associated Gazette Notification SO 988 Part II, Section 3, |
Tower Height (up to 400KV) | Within a radius of 10 km around aerodromes and air to ground firing ranges, all transmission lines and structures of height 45 meters or more shall be provided with day and night visual aids. |
Line Marker (up to 400KV) | Line Markers :Colored globules of 40-50 cm diameter made of reinforced fibber glass or any other suitable material, weighing not more than 4.5 kg each with suitable clamping arrangement and drainage holes shall be installed on the earth wire(s) in such a manner that the top of the marker is not below the level of the earth wire. Up to 400-metre span, one globule shall be provided in the middle of the span on the highest earth wire. In case of double earth wires, the globule may be provided on any one of them. For span greater than 400-metres, one additional globule may be provided for every additional 200-metre span or part thereof. Half orange and half white colored globule should be used. |
Structure Marking (up to 400KV) | Structure Marking: The structure portion excluding cross-arms above 45 m height shall be painted in alternate bands of international orange and white colours. The bands shall be perpendicular to the vertical axis and the top and bottom bands shall be orange. There shall be an odd number of bands. The maximum height of each band shall be 5 m. |
Span(up to 400KV) | Minimum ground clearance from lowest point of power conductor shall be 8 840 mm. |
Span(up to 400KV) | Minimum mid-span vertical clearance between power conductor and ground wire in still air at normal design span shall be 9 000 mm. |
Clearance (up to 400KV) | Vertical clearances above Railway Track : 220KV To 400KV =19.3 Meter |
Shield Angle (400KV) | For 440KV :Shielding Angle= 20° |
Clearance (400KV) | For 440KV :Maximum Length of Suqeusion Strings from Shackle Attachment at Hanger to Centre Line of Conductor =3 850 mm |
Clearance (400KV) | For 440KV :Maximum Length of Tension Strings from Tower Attachment to Compression Dead-End Attachment=5600mm |
Clearance (400KV) | For 440KV :Minimum Ground Clearance from Lowest Point of Power Conductor=8400mm |
Clearance (400KV) | For 440KV :Minimum Mid-Span Vertical Clearance Between Power Conductor end Ground Wire in Stilt Air=9000mm |
Clearance (400KV) | For 440KV :Right-of-way and transport requirements of maintenance, the following right-of-way width for 400 kV lines are recommended: Single/Double Circuit=50meter |
Clearance (400KV) | For 400KV Road Crossing: At all important crossings, the towers shall be fitted with normal suspension or tension insulator strings depending on the type of towers but the ground clearance at the roads under maximum temperature and in still air shall be such that even with conductor bundle broken in adjacent span, the ground clearance of the conductor from the road surface shall not be less than 8.84 meters. At all national highways tension towers shall be used. The crossing span, however, shall not exceed 25 meters in any case. |
Phase-Phase-Neutral Conductor Clearance (As per IS:5613) | ||
Voltage | Description | Distance |
Up to 650V | Horizontal “V” Shape Cross arm: (P-P(Street Light)-Neutral) | Phase to Neutral=750mm , Phase to Phase(Streetlight at Top of Pole)=325mm, Last Phase-Cross Arm end=80mm |
650V to 11KV | Horizontal Cross arm: (P-P(Street Light)-N) | Phase-Phase=300mm, Phase-Phase(Street Ltg)=300mm, Phase-Neutral=300mm, Last Phase-Cross Arm end=80mm |
Low and Medium Voltage Line | (Horizontal Configuration): | Less than 75cm Sag(P-P) =30 cm 76cm to 120 cm Sag (P-P)=45 cm 121cm to 145 cm Sag (P-P)=60 cm |
Low and Medium Voltage Line | (Vertical Configuration): | Less than 70cm Sag(P-P) =20 cm 71cm to 100 cm Sag (P-P)=30 cm |
High Voltage Line | (Horizontal Configuration): | Up to 120cm Sag(P-P) =40 cm 140cm to 225cm Sag (P-P)=65 cm Double Circuit on Same Pole at Different Level: Distance between two Circuit=120 cm |
Min Overhead conductor Clearance (Up to 11KV) (As per IS:5613) | |
Type of Crossing | Clearance |
Across any street (Low Medium Voltage) | 5.8 Meter |
Across any street (High Voltage) | 6.1 Meter |
Along with street (Low Medium Voltage) | 5.5 Meter |
Along with street (High Voltage) | 5.8 Meter |
Line(Bare) erected elsewhere(Low &Medium Voltage) | 4.6 Meter |
Line(Bare) erected elsewhere(High Voltage) | 4.6 Meter |
Line(Insulated) erected elsewhere(Low &Medium Voltage) | 4.0 Meter |
Line(Insulated) erected elsewhere(High Voltage) | 4.0 Meter |
Line conductor from buildings(Low &Medium Voltage) | 2.5 Meter |
Line conductor from buildings(High Voltage) | 3.7 Meter |
Span of Overhead Conductor (As per IS:5613) | ||
System Voltage | Number Of Circuit | Span |
33 KV (over Pole) | Single | 90 Meter to 135 Meter |
33 KV | Single | 180 Meter to 305 Meter |
33 KV | Double | 180 Meter to 305 Meter |
66 KV | Single | 204 Meter to 305 Meter |
66 KV | Double | 240 Meter to 320 Meter |
220 KV | Single | 320 Meter to 380 Meter |
220 KV | Double | 320 Meter to 380 Meter |
Clearance (11KV to 220KV) (As per IS:5613) | |||
Voltage | Number Of Circuit | P-P Vertical Clearance | P-P Horizontal Clearance |
33KV | Single | 1.5 Meter | 1.5 Meter |
33KV | Single/Double | 1.5 Meter | 1.5 Meter |
66KV | Single/Double | 2.0 Meter | 3.5 Meter |
110KV | Single/Double | 3.2 Meter | 5.5 Meter |
220KV | Single/Double | 4.9 Meter | 8.4 Meter |
Phase to Earth wire Clearance (As per IS:5613) | |
Line Voltage(KV) | Spacing between P-E |
33 KV | 1.5 Meter |
66 KV | 3.0 Meter |
110 KV | 4.5 Meter |
132 KV | 6.1 Meter |
220 KV | 8.5 Meter |
Abstract of IS:5039 for Distribution Pillar (<1KV AC&DC) | |
Distribution pillars | Distribution pillars are used by a number of distributing agencies to interconnect, terminate, control, protect and sectionalize distribution feeders. |
They are generally located on public footpaths abutting the building line or along the kerb line of footpaths. | |
The distribution pillars covered by this standard are intended to incorporate HRC type fuses/links only and of current rating not exceeding 630 amperes. | |
This standard covers distribution pillars for voltages not exceeding 1 000 V ac or 1 200 V dc, the current rating in each outgoing or incoming circuit not exceeding 630 A, for use on ac or dc systems, in outdoor conditions. | |
Rating of Individual Circuits:
| The rated current of the outgoing or incoming circuits shall be as follows: 160, 200, 250, 400 and 630 amperes. |
NOTE 1: These ratings correspond to those of fuse-bases. | |
NOTE 2 : All the incoming circuits of the same distribution pillar shall have the | |
Same current rating and similarly all the outgoing circuits of the same distribution pillar shall have the same current rating. Unless otherwise specified the sum of the rated current of the incoming circuits shall be fixed at the 2/3 of the sum of the current ratings of outgoing circuits, rounded up to the nearest higher value of the preferred current | |
Rated Diversity Factor:
| The rated diversity factor of the distribution pillar having several incoming and outgoing circuits is the ratio of the maximum sum at any one time, of the assumed circuits of all the circuits involved, to the sum of the rated currents of all the circuits of the distribution pillar. |
NUMBER OF FUSE-WAYS DIVERSITY FACTOR 2 and 3 0.9 4 and 5 0.8 6 to 9 inclusive 0.7 10 and above 0.6 | |
Enclosure:
| It shall be in all respect suitable for outdoor installations. It shall be made from a suitable material to withstand rough usage and weather. If fabricated out of MS sheets the thickness of the sheet shall be at least 3.15 mm |
Doors:
| Distribution pillars shall have a set of double hinged doors at the front. Similar doors shall be provided at the back also; if specified. |
The doors shall be so fitted as to provide the interior with maximum protection from atmospheric conditions. The hinges shall be of such construction that the doors can be swung open by not less than 150°. | |
In addition the hinged design shall permit doors being completely removed when necessary. The base horizontal member shall be completely removable to facilitate cable jointing | |
Canopy:
| The top of the pillar shall be fitted with a sloping canopy design of which shall be such that rain water shall not accumulate on the top. |
Aprons:
| If required, an apron (two if there are doors at the rear also) shall be provided below the door level of the pillar. They shall be easily removable. The apron shall be made from a suitable material to withstand rough usage. If made from sheet steel, the thickness of the sheet shall be at least 3.15 mm. |
Pillar Lighting:
| A bayonet lamp holder complying with IS : 1258-1987, with a tumbler switch, competing with IS : 3854-1988†, a three pin plug and socket complying with IS : 1293-1988 with necessary fuses and wiring shall be provided inside the pillar. |
Unless otherwise agreed between the manufacturers and user, on TPN fuse boards, terminals for the neutral conductor shall allow the connection of aluminium conductors having a current carrying capacity: | |
(a) equal to half the current carrying capacity of the phase conductor with a minimum of 25 mm2, if the size of the phase conductor exceeds 25 mm2 | |
(b) equal to the full current carrying capacity of the phase conductor if the size of the latter is less than or equal to 25mm2. | |
Bus-bar | Suitable barriers shall be provided between bus-bars |
Earthing
| The distribution pillar shall be provided with two separate earthing terminals and the framework shall be metallically connected with the casing. |
Abstract of IS:11892 | |
Maximum external Diameter of Cable (dc)= | =kc X d where d= Nominal dis of conductor standards. Kc=1 for solid cable. For stranded cable kc=3 (up to 7 stranded). More than 7 stranded kc=1.16 X sq.root(n1), n1=Number of stranded |
Abstract of IS:1445 for Porcelain Insulator | ||
Porcelain Insulator | Type A | An insulator unit in which the lengths of the shortest puncture patch through solid insulating material is at least equal to half the length of the shortest flash over path through air outside the insulator |
Type B | An insulator or an insulator unit in which the length of the shortest puncture patch through solid insulating material is less than half the length of the shortest flash over path through air outside the insulator. |
Abstract of IS: 1678 for Pole | |||
PCC Pole | Class of Pole | Length of Pole | Min Ultimate Transverse Load |
Class 1 | 17 Meter | 3000 Kg | |
Class 2 | 17 Meter | 2300 Kg | |
Class 3 | 17 Meter | 1800 Kg | |
Class 4 | 17 Meter | 1400 Kg | |
Class 5 | 16 Meter | 1100 Kg | |
Class 6 | 12.5 Meter | 1000 Kg | |
Class 7 | 12 Meter | 800 Kg | |
Class 8 | 12 Meter | 700 Kg | |
Class 9 | 11Meter | 450 Kg | |
Class 10 | 9 Meter | 300 Kg | |
Class 11 | 7.5Meter | 200 Kg | |
PCC Pole Tolerance | Tolerance: The tolerance of overall length of the poles shall be + 15 mm. | ||
The tolerance on cross-sectional dimensions shall be + 3 mm. | |||
The tolerance on cross-sectional dimensions shall be + 3 mm. | |||
The tolerance on uprightness of the pole shall be 0.5 per cent | |||
PCC Pole depth in Ground:
| Length of Pole | Min depth in ground | |
6 Meter To 7.5 Meter | 1.2 Meter | ||
8 Meter To 9 Meter | 1.5 Meter | ||
9.5 Meter To 11 Meter | 1.8 Meter | ||
11.5 Meter To 13 Meter | 2.0 Meter | ||
13.5 Meter To 14.5 Meter | 2.2 Meter | ||
15 Meter To 16.5 Meter | 2.3 Meter | ||
17 Meter | 2.4 Meter |
Abstract of IS:11171 for Transformer | |||
Transformer Temperature Rise Limit
| Part | Type of Insulation | Degree (Centigrade) |
Part=Winding | Type of Insulation=A | 50 Centigrade | |
Part=Winding | Type of Insulation=E | 65 Centigrade | |
Part=Winding | Type of Insulation=B | 70 Centigrade | |
Part=Winding | Type of Insulation=F | 90 Centigrade | |
Part=Winding | Type of Insulation=H | 115 Centigrade | |
Part=Winding | Type of Insulation=G | 140 Centigrade | |
Part= Core, MetallicPart | Type of Insulation=- | Not rise to damage core or metallic part | |
Transformer Cooling Method indication
| Type of cooling Medium: A=Air | ||
First Letter= Type of Cooling Medium (Contact with Winding) | |||
Second Letter = Kind of Circulation(Contact with Winding) | |||
Third Letter= Type of Cooling Medium (Contact with external cooling System) | |||
Forth Letter = Kind of Circulation (Contact with external cooling System) | |||
Transformer Reduce Temperature Rise Limit
| TRANSFORMER designed for operation at an altitude greater than 1 000 m but tested at normal altitudes the limits of temperature rise are reduced by the following amounts for each 500 m by which the intended working altitude exceeds 1000Meter | ||
( a) Natural-air-cooled Transformers 2.5 % (b) Forced-air-cooled Transformers % | |||
Transformer Parallel operation Condition
| (1 )Rated power ( kVA ); | ||
(2) Rated voltage ratio; | |||
(3) Voltage ratios corresponding to tappings other than the principal tapping. | |||
(4) Rated power (kVA); Rated voltage ratio; Voltage ratios corresponding to tapings other than the principal tapping. | |||
(5) Load loss at rated current on the principal tapping, corrected to the appropriate reference temperature. | |||
(6) Impedance voltage at rated current ( on the principal tapping ). | |||
(7) Short-circuit impedances, at least on the extreme tappings, if the tapping. Range of the tapped winding exceeds + or – 5 %. |