Low Voltage Power Compensation Products
Alstom Grid’s compensation equipment helps customers improve performance through energy savings and better power quality. With our products and solutions customers save money and reduce the environmental impact of their operations.
Low Voltage Capacitor Units
Low voltage capacitor units are manufactured by using the latest methods. Capacitor elements of metallized polypropylene film are self-healing and dry without impregnation liquid. Each capacitor element is individually protected with patented internal protection. Capacitors have low losses and are constructed to be light in weight
DW-Series Detuned Filter Capacitor Banks
Alstom Grid’s DW-series automatic capacitor banks with blocking reactors are intended for power factor correction in systems where harmonic distortion is present. New modular and compact design provide space saving and flexible mounting options for wall or floor mounting. DW-series is available in two variants, standard and extension. Extension types includes space for fast and easy power extension. Reactive power compensation is controlled with high performance reactive power controller N-6
Automatic Detuned Filter Capacitor Banks
Power transmission and distribution systems are designed to operate with sinusoidal voltage and current waveforms at a constant frequency. However, when nonlinear loads – such as thyristor drives, converters and arc furnaces – are connected to the system, excessive harmonic currents are generated, and this causes both current and voltage distortion. Power factor correction by means of conventional capacitor banks is not possible in systems affected by harmonics. This is because the harmonic-currents are amplified in the parallel resonant circuit formed by the capacitor and the network. As a result current and voltage distortion are further increased.
When harmonics are presented in the system, power factor correction should be implemented by means of automatic capacitor banks with blocking reactors. Each step of the bank consists of a capacitor unit with a blocking reactor. These form a series resonant circuit tuned to a frequency below that of the lowest harmonic.
Harmonic Filters
Harmonic filters consist of capacitors connected in series with a reactor. Capacitors produce reactive power at the filter's fundamental frequency ant the circuit is designed to achieve the required power factor correction. The inductance of the reactor is chosen so that the filter forms a very low impedance series resonant circuit at the harmonic frequency. This ensures that a high proportion of the harmonics enter the filter. A typical harmonic filter consist of three series resonant circuits tuned to the most common harmonics (5th, 7th and 11th harmonics). The filters are housed in steel cubicles. Each consists of a contactor, thermal over current relay, reactor and capacitors. The unit is generally connected to the fused feeders on the main distribution board.
Third Harmonic Filter
Nonlinear one-phase loads such as fluorescent illuminators and computers which are connected between phase and neutral are generating third harmonic and multiple of it. All harmonic currents cause both current and voltage distortion. In addition to this third harmonic currents accumulate in the neutral wire increasing the risk of overloading and caused magnetic field having frequency of 150 Hz. By filtering third harmonic from the network the above mentioned problems can be eliminated.
3rd harmonic filter consists of capacitor units which are connected in series with reactors. The harmonic filter produces reactive power at fundamental frequency in order to reach the target power factor. The inductance of the reactor has been chosen to create very low impedance series resonance circuit for 3rd harmonic. As a result of this most of 3rd harmonic current can be filtered. The filter cubicle has a contactor, a thermal overload relay, reactors, capacitors and a voltage control relay
Thyristor Switched Capacitor Banks (TSC)
Thyristor switched capacitor banks equipped with a fast control are designed to support the line voltage and to compensate the reactive power of the load. Thyristor switches make possible that a fast response is achieved without any mechanical wear, noise or excessive transient associated with contactor switching. A control signal can be brought from the compensated equipment and so it is achieved reactive power compensation almost without delay. All steps of the capacitor bank are switched on during one network period. Each step of the bank consists of a capacitor unit with a blocking reactor. These form a series resonant circuit tuned to a frequency below that of the lowest harmonic.
Capacitor bank is chosen to be suitable for load according to the control system, compensation power and load switching. The compensated equipment can be symmetrical or unsymmetrical for main or phase voltage switched loads.
Fixed Detuned Filters
Fixed detuned filters are used to compensate the reactive power in individual, standard-power devices or groups of devices in networks affected by harmonics. A fixed detuned filter consists of a reactor connected in series with the power capacitor unit. With this construction a resonance phenomenon between network inductance and capacitor capacitance is avoided.
A fixed detuned filter is usually connected in parallel with the device or the group of devices to be compensated. In this way, the capacitor is switched on and off simultaneously with the load. When necessary, a contactor can be installed inside the box in a case when the detuned filter is wanted to be controlled separately.
High Voltage Power Compensation Products
High voltage capacitor units have all-film dielectric and are impregnated with dielectric liquid which is environmentally safe. Each capacitor element has a separate internal fuse. In addition each capacitor is provided with an internal discharge resistor.
All capacitors have low losses and are constructed to be light in weight. The high voltage power capacitors comply with most national and international capacitor standards.
Enclosed Capacitor Banks
Enclosed capacitor banks are designed by Alstom Grid for power factor correction, voltage support and harmonic suppression in medium voltage distribution systems. They supply continuous, group or central reactive power compensation of fluctuating loads in three-phase networks up to 36kV. The banks are manufactured in two basic types: fixed and automatic.
The enclosed capacitor banks are designed for indoor and outdoor mounting arrangements. The protection class of the enclosures ranges from IP30 to IP54. The system can be fitted with various options to meet virtually all customer needs such as damping or detuned reactors, different ventilation systems and key interlocking systems, earthing switches etc.
Harmonic FIlters for High Voltage
Power Transmission and distribution systems are designed for operation with sinusoidal voltage and current waveforms at a constant frequency. However, when non-linear loads - such as thyristor drives, converters and arc furnaces - are connected to the system, excessive harmonic currents are generated, and this causes both current and voltage distortion. Harmonic filters represent the optimum solution to distortion problems. Consisting of capacitors, reactors and resistors, filter circuits provide a low impedance route out of the system for harmonics. Distortion is reduced to the required levels. Single-tuned, double-tuned and high-pass filters are all available. At the fundamental frequency (50 or 60 Hz) the filter acts as capacitor and produces reactive power , functioning in the same way as a conventional capacitor bank.
Air-Core Reactors
Air-Core Reactors (ACR) provide a linear response of impedance versus current which is essential for numerous applications. The dry type design is maintenance free and environmentally friendly.
Alstom Grid has more than 50 years’ experience in designing and manufacturing Air-Core Reactors for various market segments around the world, including power generation, T&D networks, industrial facilities, OEMs and electrical test laboratories.
For both industrial environments and networks, Alstom Grid offers a broad range of cost-effective solutions:
• Current-limiting reactors limit the fault currents to levels compatible with existing protection/control equipment and as a result provide for a very cost-effective solution.
• Neutral-earthing reactors are connected between the neutral of a power system and earth to limit the line-to-earth current to a desired value under system earth fault conditions.
• Smoothing reactors reduce the harmonic currents and transient overcurrents (ripple) in DCsystems.
• Harmonic filter reactors are usually connected with capacitors and resistors in filter circuits to reduce harmonic content in the network which cause higher losses, high neutral currents and interference with computer and telecommunications equipment and which are responsible for high harmonic distortion levels.
• Shunt reactors compensate for the capacitive currents of long transmission lines or cables, allowing more active energy to pass through the system.
• Damping reactors limit the inrush and outrush currents of capacitor banks.
• Discharge reactors are used in the bypass/discharge circuit in series compensation systems to limit the capacitor discharge current.
• Arc-furnace series reactors provide the necessary power factor correction and limit the unstable arc-furnace current and voltage.
• Power flow control reactors control the current into two or more parallel circuits.
• Motor starting reactors are connected in series with a motor to limit the inrush current during the motor starting operation.
• Special applications: test lab reactors are special ACRs used in test laboratories, mainly for current-limiting purposes. Other devices include duplex current-limiting reactors.
Electronic products
Power factor controllers
Power factor controllers models for 6 or 12 steps are designed and manufactured to control automatic capacitor banks. They provide your network with efficient reactive power compensation, measuring, supervision and communication features. They are modular, robust, compact, programmable and easy to install and to use.
Unbalance Current Protection Relays NUR-36
Protective relay NUR-36 is a single phase, sensitive, over-current relay. It features two stages of over-current protection, both having their own parameters and output relays. The NUR-36 is designed for unbalance current protection of double-star (Y-Y) connected capacitor banks in high voltage applications. It has solid state construction and is suitable for panel installation (DIN 43700). The relay has filters for harmonic currents and operate at fundamental frequency only. Protection is tested according to IEC 255-5c, 255-22-2 class III, 801-4 class III and the product fulfils the CE requirements. Information about measurements and relay functions is given by digital display and LED's.
Capacitance Meter NCM-20
Capacitance Meter type NCM-20 is designed to measure capacitor units in a capacitor bank without removing any connecting wire between separate capacitor units. This measurement is used to locate blown fuses in the units. NCM-20 is battery operated and portable comprising a separate display and generator untis and is well suited for field use. The measured capacitance is displayed by a 3 ½-digit LCD-display on the display unit. The generator unit includes a built-in calibration capacitor.