Oil insulated Outdoor Instrument Transformers Buyer’s Guide Table of content Page Products Introduction 3 Explanations 4 Silicone Rubber (SIR) Insulators 7 Design features and Advantages Current transformers IMB 8 Inductive voltage transformers EMF 10 Capacitor voltage transformers CPB 12 Coupling capacitors CCB 14 Technical Technical catalogues: information Current transformers IMB 17 Inductive voltage transformers EMF 33 Capacitor voltage transformers CPB 41 Coupling capacitors CCB 53 Optional PQSensor™ 60 Cable entry kits - Roxtec CF 16 64 Quality, control and testing 66 Inquiry and ordering data 68 2 Outdoor Instrument Transformers | Buyer’s Guide Day after day, all year around— with ABB Instrument Transformers ABB has been producing instrument transformers for All instrument transformers supplied by ABB are tailor- more than 70 years. Thousands of our products perform made to meet the needs of our customers. vital functions in electric power networks around the An instrument transformer must be capable of world – day after day, all year round. withstanding very high stresses in all climatic conditions. Their main applications include revenue metering, control, We design and manufacture our products for a service life indication and relay protection. of at least 30 years. Actually, most last even longer. Product range Type Highest voltage for equipment (kV) Current Transformer IMB Hairpin/Tank type IMB 36 - 800 36 - 800 Paper, mineral oil insulation, quartz filling Inductive Voltage Transformer EMF Paper, mineral oil insulation, quartz filling EMF 52 - 170 52 - 170 Capacitor Voltage Transformer CPB CVD: Mixed dielectric polypropylene-film and synthetic oil. CPB 72 - 800 72.5 - 800 EMU: Paper, mineral oil Coupling Capacitors CCB Mixed dielectric polypropylene-film and synthetic oil. CCB 72 - 800 72.5 - 800 We are fexible and tailor make each instrument transformer to our customers needs. Sizes other than those mentioned above can be supplied upon request. Buyer’s Guide | Outdoor Instrument Transformers 3 Explanations Technical specifcations - General Standard frequencies are 50 Hz and 60 Hz. Standard/Customer specification There are international and national standards, as well as cus- Other frequencies, such as 16 2/3 Hz and 25 Hz might be ap- tomer specifcations. ABB High Voltage Products can meet most plicable for some railway applications. requirements, as long as we are aware of them. When in doubt, please enclose a copy of your specifcations with the inquiry. Ambient temperature Average 24 hours ambient temperature above the standard- System voltage ized +35 °C influences the thermal design of the transformers The system voltage is the maximum voltage (phase-phase), and must therefore be specified. expressed in kV rms, of the system for which the equipment is intended. It is also known as maximum system voltage. Installation altitude If installed >1000 m above sea level, the external dielectric Rated insulation level strength is reduced due to the lower density of the air. Always The combination of voltage values which characterize the specify the installation altitude and normal rated insulation insulation of an instrument transformer with regard to its ca- levels. ABB will make the needed correction when an altitude pability to withstand dielectric stresses. higher than 1000 meters ASL is specified. Internal insulation is not affected by installation altitude and dielectric routine tests The rated value given is valid for altitudes ≤1000 m above sea will be performed at the rated insulation levels. level. A correction factor is introduced for higher altitudes. Creepage distance Lightning impulse test The creepage distance is defined as the shortest distance The lightning impulse test is performed with a standardized along the surface of an insulator between high voltage and wave shape – 1.2/50 µs – for simulation of lightning overvoltage. ground. Rated Power Frequency Withstand Voltage The required creepage distance is specified by the user in: This test is to show that the apparatus can withstand the − mm (total creepage distance) power frequency over-voltages that can occur. − mm/kV (creepage distance in relation to the highest system voltage). The Rated Power Frequency Withstand voltage indicates the required withstand voltage. The value is expressed in kV rms. Pollution level Environmental conditions, with respect to pollution, are some- Rated SIWL times categorized in pollution levels. Five pollution levels are For voltages ≥300 kV the power-frequency voltage test is described in IEC 60815-1. partly replaced by the switching impulse test. The wave shape 250/2500 µs simulates switching over-voltage. There is a relation between each pollution level and a corre- sponding minimum nominal specific creepage distance. The rated Switching Impulse Withstand Level (SIWL) indi- cates the required withstand level phase-to-earth (phase- Pollution level Creepage distance Creepage distance (Old) to-ground), between phases and across open contacts. The Phase - Ground voltage Phase - Phase voltage value is expressed in kV as a peak value. mm/kV mm/kV a - Very light 22.0 - Rated Chopped Wave Impulse Withstand voltage, b - Light 27.8 16 Phase-to-earth c - Medium 34.7 20 The rated chopped wave impulse withstand level at 2 µs d - Heavy 43.3 25 and 3 µs respectively, indicates the required withstand level e - Very Heavy 53.7 31 phase-to-earth (phase-to-ground). Rated frequency Wind load The rated (power) frequency is the nominal frequency of the The specifed wind loads for instrument transformers intended for system expressed in Hz, which the instrument transformer is outdoor normal conditions are based on a wind speed of 34 m/s. designed to operate in. 4 Explanations | Buyer’s Guide Current transformers Secondary reconnection Currents Extra secondary terminals (taps) are taken out from the sec- The rated currents are the values of primary and secondary ondary winding. The load capacity drops as the ampere-turns currents on which performance is based. decrease on the taps, but the short-circuit capacity remains constant. Each core can be individually reconnected. Rated primary current The rated current (sometimes referred to as rated current, Burden and Accuracy Class (IEC) nominal current or rated continuous current) is the maximum Burden continuous current the equipment is allowed to carry. The external impedance in the secondary circuit in ohms at The current is expressed in A rms. the specified power factor. It is usually expressed as the ap- parent power – in VA -, which is taken up at rated secondary The maximum continuous thermal current is based on average current. It is important to determine the power consumption 24 h ambient temperature of +35 °C. of connected meters and relays including the cables. Unnec- essarily high burdens are often specified for modern equip- It should be selected about 10 - 40% higher than the esti- ment. Note that the accuracy for the measuring core, accord- mated operating current. Closest standardized value should ing to IEC, can be outside the class limit if the actual burden be chosen. is below 25% of the rated burden. Extended current ratings Accuracy A factor that multiplied by the rated current gives the maxi- The accuracy class for measuring cores is according to the mum continuous load current and the limit for accuracy. Stan- IEC standard given as 0.2, 0.2S, 0.5, 0.5S or 1.0 depending dard values of extended primary current are 120, 150 and on the application. For protection cores the class is normally 200% of rated current. Unless otherwise specified, the rated 5P or 10P. Other classes are quoted on request, e.g. class continuous thermal current shall be the rated primary current. PR, PX, TPS, TPX or TPY. Rated secondary current Rct The standard values are 1, 2 and 5 A. 1 A gives an overall The secondary winding resistance at 75 °C lower burden requirement through lower cable burden. Instrument Security Factor (FS) Rated short-time thermal current (I ) To protect meters and instruments from being damaged by th The rated short-time withstand current is the maximum cur- high currents, an FS factor of 5 or 10 is often specified for rent (expressed in kA rms) which the equipment shall be able measuring cores. This means that the secondary current will to carry for a specified time duration. increase maximum 5 or 10 times when the rated burden is connected. FS10 is normally sufficient for modern meters. Standard values for duration are 1 or 3 s. I depends on the th short-circuit power of the grid and can be calculated from the Accuracy Limit Factor (ALF) formula: I = P (MW) / U (kV) x √3 kA. The protection cores must be able to reproduce the fault cur- th k m rent without being saturated. Rated dynamic current (I ) The overcurrent factor for protection cores is called ALF. dyn The dynamic short-time current is according to IEC, ALF = 10 or 20 is commonly used. I = 2.5 x I and according to IEEE, I = 2.7 x I dyn th dyn th Both FS and ALF are valid at rated burden only. If lower bur- Reconnection den the FS and ALF will increase. The current transformer can be designed with either primary or secondary reconnection or a combination of both to obtain Burden and Accuracy Class for other standards, such as more current ratios. ANSI, IEEE, etc. More detailed information about standards other than IEC Primary reconnection can be found in our Application Guide, Outdoor Instrument The ampere-turns always remain the same and thereby the Transformers, Catalog Publication 1HSM 9543 40-00en or in load capacity (burden) remains the same. The short-circuit ca- the actual standard. pacity however may be reduced for the lower ratios. Primary reconnection is available for currents in relation 2:1 or 4:2:1. Buyer’s Guide | Explanations 5 Explanations Voltage transformers Thermal limit burden Voltages Thermal limit burden is the total power the transformer can The rated voltages are the values of primary and secondary supply without excessively high temperature rise. The trans- voltages on which the performance is based. former is engineered so that it can be loaded with the imped- ance corresponding to the load at rated voltage, multiplied by Voltage factor (FV) the square of the voltage factor. This means that at a voltage It is important that the voltage transformer, for thermal and factor of 1.9/8h, for example, the limit burden = total rated protection reasons, can withstand and reproduce the continu- burden x 1.92. ous fault overvoltages that can occur in the net. The over- The transformer cannot be subjected to a higher limit burden voltage factor is abbreviated as FV. without being loaded higher than the rated burden. Conse- quently, because of loading considerations, it is unnecessary The IEC standard specifies a voltage factor of 1.2 continu- to specify a higher thermal limit burden. ously and simultaneously 1.5/30 sec. for systems with effec- tive grounding with automatic fault tripping, and 1.9/8 hrs for Voltage drop systems with insulated neutral point without automatic ground The voltage drop in an external secondary circuit (cables and fault systems. fuses) can have a significantly larger influence on the system ratio error than incorrect burden. Accuracy, according to IEC, for measuring windings is fulfilled between 0.8 and 1.2 x rated voltage and for protection wind- Ferroresonance ings up to the voltage factor (1.5 or 1.9 x rated voltage). Ferroresonance is a potential source of transient overvoltage. Three-phase, single-phase switching, blown fuses, and bro- Reconnection ken conductors can result in overvoltage when ferroresonance The voltage transformer can be designed with secondary occurs between the magnetizing impedance of a transformer reconnection. and the system capacitance of the isolated phase or phases. Secondary reconnection means that extra secondary termi- For example, the capacitance could be as simple as a length nals (taps) are taken out from the secondary winding(s). of cable connected to the ungrounded winding of a trans- former. Another example of ferroresonance occurring is when Burden and accuracy class an inductive voltage transformer is connected in parallel with Burden a large grading capacitor across the gap of a circuit breaker. The external impedance in the secondary circuit in ohms at the specified power factor. It is usually expressed as the ap- Ferroresonance is usually known as a series resonance. parent power – in VA -, which is taken up at the rated sec- ondary voltage. Additional for Capacitor Voltage Transformers (CVT) and (See Current Transformers above). Capacitor Voltage Divider (CVD) Capacitance phase - ground The accuracy class for measuring windings, according to IEC, Requirements for capacitance values can be applicable when is given as 0.2, 0.5 or 1.0 depending on the application. A using the CVT for communication over lines (for relay func- rated burden of around 1.3-1.5 times the connected burden tions or remote control). will give maximum accuracy at the connected burden. PLC = Power Line Carrier. Higher capacitance => Smaller impedance for signal. For protection purposes the class is normally 3P or 6P The ABB line matching unit can be adjusted to any capaci- tance within frequency range 50-500 kHz. Simultaneous burden (IEC) Metering windings and protection windings not connected in The lower applied frequency decide the minimum capacitance open delta are considered as simultaneously loaded. A pro- of coupling capacitor. tection winding connected in open delta is not considered as a simultaneous load. More information regarding instrument transformers More detailed information about instrument transformers can be found in our Application Guide, Outdoor Instrument Trans- formers. Catalog Publication 1HSM 9543 40-00en 6 Explanations | Buyer’s Guide Silicone Rubber Insulators Wide range of instrument transformers with silicone rubber ABB manufacturing technique (SIR) insulators The patented helical extrusion moulded silicone rubber insula- ABB can supply most of our instrument transformers with tors without joints (chemical bonds between spirals) mini- patented helical extrusion-moulded silicone rubber insulation. mizes electrical field concentrations and reduces build-up of contamination. The cross-laminated fiberglass tube inside the CT IMB 36 - 800 kV insulator provides high mechanical strength. VT EMF 52 - 170 kV CVT CPB 72 - 800 kV Completed tests CC CCB 72 - 800 kV The silicone material used for ABB Instrument Transformers is approved according to IEC and ANSI/IEEE standards. Why Silicone Rubber Insulators? Tests performed: Ceramic (porcelain) insulators have performed well for several de- − Accelerated ageing test (1000 h) cades, but one of the disadvantages with porcelain is its fragility. − Lightning impulse test, wet power frequency test and wet switching impulse test Listed below are some of the advantages of silicone rubber − Short circuit test insulators compared to porcelain: − Temperature rise test − Non-brittle Color − Minimum risk for handling and transport damages The (SIR) insulators for the instrument transformers are sup- − Minimum risk for vandalism plied in a light gray color. − Light-weight − Explosion safety Deliveries − Excellent pollution performance ABB in Ludvika has supplied instrument transformers with − Minimum maintenance in polluted areas (SIR) insulators for the most severe conditions, from marine − Hydrophobic climate to desert and/or polluted industrial areas. A reference list can be provided on request. There are several polymeric insulator materials available, of which silicone has proven to be superior. Comparison of polymeric insulators Epoxy EP-rubber Silicone Brittle Low Excellent Excellent Insulation Fair Good Excellent Weight Good Excellent Excellent Mechanical strength Excellent Good Excellent Safety Good Good Excellent Earthquake Good Excellent Excellent Handling Good Excellent Excellent Maintenance Fair Fair Excellent Ageing Fair Good Excellent UV-resistance Good Good Excellent Experience of material ABB has used silicone rubber (SIR) insulators since 1985, starting with surge arresters, and has gained considerable experience thereof. Buyer’s Guide | Outdoor Instrument Transformers 7 IMB Design features and advantages ABB’s oil minimum current transformers type IMB is based Impregnation on a hairpin design (shape of the primary conductor) also Heating in a vacuum dries the windings. After assembly all known as tank type. The basic design has been used by free space in the transformer (approx. 60%) is filled with clean ABB for more than 70 years, with more than 170 000 units and dry quartz grain. The assembled transformer is vacuum- delivered. treated and impregnated with degassed mineral oil. The trans- former is always delivered oil-filled and hermetically sealed. The design corresponds with the demands of both the IEC and IEEE standards. Special design solutions to meet other Tank and Insulator standards and/or specifications are also available. The lower section of the transformer consists of an aluminum tank in which the secondary windings and cores are mounted. The unique filling with quartz grains saturated in oil gives a The insulator, mounted above the transformer tank, consists resistant insulation in a compact design where the quantity of as standard of high-grade brown-glazed porcelain. Designs oil is kept to a minimum using light gray porcelain or silicon rubber can be quoted on request. The IMB transformer has a very flexible design that, for ex- ample, allows large and/or many cores. The sealing system consists of O-ring gaskets. Primary winding Expansion system The primary winding consists of one or more parallel conduc- The IMB has an expansion vessel placed on top of the insula- tor of aluminum or copper designed as a U-shaped bushing tor. A hermetically sealed expansion system, with a nitrogen with voltage grading capacitor layers. cushion compressed by thermal expansion of the oil, is used The insulation technique is automated to give a simple and in the IMB as the standard design. An expansion system with controlled wrapping, which improves quality and minimizes stainless steel expansion bellows can be quoted on request. variations. On request – Capacitive voltage tap The conductor is insulated with a special paper with high The capacitive layers in the high voltage insulation can be mechanical and dielectric strength, low dielectric losses and utilized as a capacitive voltage divider. A tap is brought out good resistance to ageing. from the second to last capacitor layer through a bushing on the transformer tank (in the terminal box or in a separate box, This design is also very suitable for primary windings with depending on the IMB tank design). An advantage of the ca- many primary turns. This is used when the primary current is pacitive terminal is that it can be used for checking the condi- low, for instance unbalance protection in capacitor banks. tion of the insulation through dielectric loss angle (tan delta) (Ex. ratio 5/5 A) measurement without disconnecting the primary terminals. The tap can also be used for voltage indication, synchronizing Cores and secondary windings or similar purpose, but the output is limited by the low capaci- The IMB type current transformers are flexible and can nor- tance of the layers. mally accommodate any core configuration required. The load connected must be less than 10 kohms and the tap Cores for metering purposes are usually made of nickel alloy, must be grounded when not in use. which features low losses (= high accuracy) and low satura- tion levels. One model of IMB 72 - 123 is provided with a DDF (Dielectric Dis- sipation Factor) terminal in the secondary terminal box. The The protection cores are made of high-grade oriented steel terminal must be connected to ground during normal service, but strip. Protection cores with air gaps can be supplied for spe- can be disconnected from ground and used for checking the cial applications. dielectric dissipation factor of the internal high voltage insulation between primary terminals and ground The secondary winding consists of double enamelled cop- per wire, evenly distributed around the whole periphery of the core. The leakage reactance in the winding and also between extra tapping is therefore negligible. 8 Outdoor Instrument Transformers | Buyer’s Guide Climate 1 The transformers are designed for, and are installed in, widely 8 shifting conditions, from polar to desert climates all over the 9 2 world. Service life The IMB transformer is hermetically sealed and the low and 10 even voltage stress in the primary insulation gives a reliable product with expected service life of more than 30 years. The 3 IMB and its predecessors have since the 1930s been supplied in more than 170 000 units. Expansion system The expansion system, with a nitrogen gas cushion, increases operating reliability and minimizes the need of maintenance 4 and inspections. This type of expansion system can be used in the IMB since the quartz filling reduces the oil volume and a relatively large gas volume minimizes pressure variations. For higher rated currents an expansion vessel with external cooling fins is used to increase the cooling area and heat dis- sipation to the surrounding air. An expansion system with gas-filled stainless steel expansion units surrounded by the oil and compressed by oil expansion can be quoted on request. Quartz filling Minimizes the quantity of oil and provides a mechanical sup- port for the cores and primary winding during transport and in the event of a short-circuit. 5 Flexibility The IMB covers a wide range of primary currents up to 4 000 A. It can easily be adapted for large and/or many cores by in- 6 creasing the volume of the tank. 7 Resistance to corrosion The selected aluminum alloys give a high degree of resistance 11 to corrosion, without the need of extra protection. Anodized parts for IMB 36-170 kV can be offered on request, for use in Current Transformer IMB extreme environments. IMB >170 kV can be delivered with a protective painting. 1 Gas cushion 7 Capacitive voltage tap Seismic strength 2 Oil filling unit (hidden) (on request) The IMB has a mechanically robust construction, designed to 3 Quartz filling 8 Expansion vessel withstand high demands of seismic acceleration without the 4 Paper-insulated primary 9 Oil sight glass need of dampers. conductor 10 Primary terminal 5 Cores/secondary windings 11 Ground terminal 6 Secondary terminal box Buyer’s Guide | Outdoor Instrument Transformers 9 EMF Design features and advantages ABB’s inductive voltage transformers are intended for The insulator, in its standard design, consists of high quality, connection between phase and ground in networks with brown glazed porcelain. The voltage transformers can also be insulated or direct-grounded neutral points. supplied with silicone rubber insulators. The design corresponds with the requirements in the IEC and Expansion system IEEE standards. Special design solutions to meet other stan- The EMF has an expansion vessel placed on the top section dards and customer requirements are also possible. of the porcelain. The EMF has a closed expansion system, The transformers are designed with a low flux density in the without moving parts and with a nitrogen cushion, that is core and can often be dimensioned for 190% of the rated compressed by the expansion of the oil. A prerequisite for this voltage for more than 8 hours. is that the quartz sand filling reduces the oil volume, and the use of a relatively large gas volume, which gives small pres- Primary windings sure variations in the system. The primary winding is designed as a multi-layer coil of double enamelled wire with layer insulation of special paper. Ferro-resonance Both ends of the windings are connected to metal shields. The design of the EMF notably counteracts the occurrence of ferro-resonance phenomena: Secondary and tertiary windings In its standard design the transformer has a secondary − The low flux in the core at the operating voltage gives a measurement winding and a tertiary winding for ground fault large safety margin against saturation if ferro-resonance protection, but other configurations are available as required. oscillations should occur. (2 secondary windings in a design according to IEEE standard) − The flat magnetization curve gives a smooth increase of The windings are designed with double enamelled wire and core losses, which results in an effective attenuation of the are insulated from the core and the primary winding with ferro-resonance. pressboard (presspahn) and paper. The windings can be equipped with additional terminals for If the EMF transformer will be installed in a network with other ratios (taps). a high risk for ferro-resonance, it can, as a further safety precaution, be equipped with an extra damping burden, on a Core delta connected tertiary winding. See the figure below. The transformer has a core of carefully selected material, to give a flat magnetization curve. The core is over-dimensioned R with a very low flux at operating voltage. S T Impregnation Heating in a vacuum dries the windings. After assembly, all A N A N A N free space in the transformer (approximately 60%) is filled with clean and dry quartz grains. The assembled transformer is a n a n a n vacuum-treated and impregnated with degassed mineral oil. The transformer is always delivered oil-filled and hermetically sealed. da dn da dn da dn Tank and insulator 60 ohm, 200 W EMF 52-170: The lower section of the transformer consists of an aluminum tank in which the winding and core are placed. The tank consists of selected aluminum alloys that give a high degree of resistance to corrosion, without the need of extra protection. Anodized aluminum can be offered on request. The sealing system consists of O-ring gaskets. Damping of ferro-resonance 10 Outdoor Instrument Transformers | Buyer’s Guide