Sanelec Excitation Systems (P) Ltd.

Peenya Industrial Area, Bangalore, Karnataka

The Digital Static Excitation system being offered is intended for providing excitation power supply directly to the main field of alternator through the slip rings. The excitation system is built around the latest technology Digital controllers of REIVAX. The digital controller provides all necessary controls, limiters and protection (related to excitation) to enable the alternator run in solo, parallel and grid parallel modes. The output of the controller is fed to the 6 pulse   firing card designed and manufactured by Sanelec. The firing card generates firing pulses for all the six thyristors employed in the power circuit. The power circuit consists of six nos of power thyristors, configured from a 3 phase bridge, mounted on massive heat sinks and interconnected by bus bars. The thyristors are rated to have sufficient voltage and current margins in order to ensure high reliability. The power circuit is force cooled by a high power panel mounted fan, in order to keep the heat sinks cool. The power output voltage of the thyristor bridge will go both positive and negative. The negative field output will help alternator to recover fast after a load throw off. The power input to the bridge will be the secondary voltage of a 3 phase excitation transformer. The secondary voltage will be rated to give adequate field forcing required for transfer conditions. Power input is applied through a power contactor. A crow bar circuit is provided across the main field to contain any induced over voltage. The crow bar is also turned ON under excitation OFF conditions. The resistor box provided in series with the crow bar will be designed to dissipate stored energy of the main field. The firing circuit employed is capable of providing firing pulses from residual voltage of the alternator. However, a separate field flashing circuit is provided to boost the residual voltage in order to enable firing circuit to put out firing pulses for the thyristor bridge. A dedicated high energy surge suppressor is provided in the system which will be connected directly across the main field or power output. This will protect the bridge thyristors and the insulation of the main field. The Digital Static Excitation System is offered in various types like single controller single power circuit, Single controller redundant power circuit, Dual Controller Dual Power circuit, Dual Controller single power circuit

MAIN ADVANTAGES OF SANELEC-REIVAX DIGITAL AVR PANELS This Digital AVR is a  3 part system :  HMI; Digital Controller; Power module .  Advantageous because Even if HMI goes out of order, AVR performance/output is not affected.. Digital controller is completely isolated from the power module. As the power module is directly connected to exciter field and input power source, any external high voltages cannot damage the costly/valuable digital controller. The power module with firing control is made in SANELEC, India. So, this 3 part system is a major advantage from  reliability, service support and cost- effective spares replacement/services  point of view Same Digital AVR  can be used  for any rating of alternator between 1MW to 100MW or more..  based on the DC excitation current and voltage Only the separate power module(consisting of IGBT/Thyristors) is changed depending on excitation rating. This is a  latest technology Digital AVR  using Texas Instruments make, Digital Signal Processor(DSP).. Power System Stabilizer(PSS-2B model) hardware is already in-built  in this controller. Depending on future government regulations, it can be enabled with software calculations & settings at a later stage(if applicable) with some extra charges.. Step-response feature , which will help with tuning of stability parameters during commissioning at no-load itself(suitable for load conditions). This will avoid frequent tripping and trials on-load during commissioning. 4nos user configurable auxiliary relays  are available for excitation related protections. Real time supervision of alternator Power Capability Curve  is available in this controller.. which will help in setting and checking the limiters activation.. Real time Trending  feature is available in this Digital Controller.. Initial excitation process  with controlled voltage build-up(Soft-start), integrated with field flashing command (in-built process in Digital Controller.) Sequence of Event Recording  is another major advantage in a digital AVR because it helps with recording/saving and troubling shooting of the events that would have happened within fraction of a second during any trip or failure.. IRIG-B time synchronism  feature in Digital Controller will enable the product to work in time synchronism (i.e., at same time zones and scales) of other equipment in the power system. Digital Input / Output contact status  is indicated by LEDs on the Digital AVR. User/Operator friendliness . Even though the Digital AVR panel comes with a HMI (Human Machine Interface) through which all commands can be given to Digital AVR, we also give panel push buttons and switches for easy access to operator. In the same way, all the limiters activation and alarms are visible in HMI through LED indications but we give Facia and Annunciator circuit with hooter, for operators visibility from long distance. Software is also user friendly

This AVR is suitable for brushless generators upto 320kVA of all makes like Kirloskar, Leroysomer, Marathon, Trident, Stamford. This AVR is a compact high performance encapsulated unit with latest technology and efficient Semiconductors to achieve a high degree of miniaturisation. This AVR contains a solid state buildup circuitry to ensure positive voltage buildup from very low residual voltages. This AVR employs true average sensing circuit, dv/dt, snubbers and special filter circuits to cope with Non-Linear loading like Batter Chargers, DC drives etc. The AVR regulates the Line to Neutral of generator voltage and in addition to this it includes under speed protection to prevent the generator rotating parts from over heating due to over fluxing. The recovery time on sudden loading is likely to be around 0.5 sec to recover 98% of the rated voltage.

The Type-A Excitation Control Panel is to provide controls and protection for the excitation control of Generators upto 30MW. The system is built around a heavy duty type Automatic Voltage Regulator and one Manual channel. AVR maintains generator voltage within close regulation limits on loading. The manual channel is built to provide excitation power upto 110% full load. The Manual channel will be useful especially during initial commissioning stages and to provide a simple alternative to the Auto channel when the Auto channel goes out of order. The VAr/PF Control Module of Sanelec is employed to provide a constant PF or constant VAr operation while operating in parallel with grid during Auto mode. This module will keep the Power Factor or VAr (depending on the mode selected) constant at the set value against normal grid voltage variation and MW load variation. The limiter used is UMVAr which protects the generator by quickly increasing the excitation when the generator Pf goes leading beyond limit. The protections are used in the event of Over Voltage, Under Voltage, Over Excitation, Under Excitation, Diode Failure and PT Fuse Failure. Indicators are provided for all operating status and fault status through µP based Facia cum Annunciator unit. The Excitation System includes features, which will enable the Generator to operate 1. Solo  2. Parallel with other Generators 3. Parallel with the EB grid MOUNTING PLATE Mounting Plate – A cost effective Analogue AVR cum APFC mounting plate for smaller range machines wherein the mounting plate can be fixed in Generator Control panels.

The Digital Excitation Control System is intended for providing controls and protection for the Excitation control of HT & LT AC Generators. The Digital Excitation Control Panel provides necessary controls and protection to operate the Generator in 1. Solo mode 2. Parallel with other generators 3. Parallel with the EB grid The system is built around AVR-01(Energy Line) or Power line controllers of REIVAX make, which has multiple control functions. The digital AVR has a soft start feature with a user-adjustable setting to govern the rate at which the generator voltage is allowed to buildup. The output voltage of AC generator is maintained at the set point by controlling the exciter field current. The AVR-0 has got one auto and one manual mode i.e. Field Current Regulator mode (FCR mode). This FCR mode will be useful at the time of commissioning and when the Auto mode operation develops problem. The VAr / Pf control module of the Digital AVR is employed to provide a constant Pf or Constant VAr operation when operating in parallel with the Grid during Auto mode. This module will keep the Power Factor / VAr constant (depending on the mode selected) at the set value against normal grid voltage variation and MW load variation. The limiters used are Minimum Excitation and Maximum Excitation Limiter. The UEL (Under Excitation Limiter) protects the generator by quickly increasing the excitation should the generator Pf goes leading beyond limit where the Generator could slip out of synchronization. The Stator Current limiter (SCL) puts a limit to the stator current (lag) and will not allow the generator to be over excited to the point of damaging the generator field windings. The protection features offer fully adjustable tripping levels and time delays. The protection features provided are i) Generator Over Voltage ii) Generator Under Voltage iii) Field Over Voltage iv) Field Over current v) Loss of sensing vi) Loss of field and vii) Exciter diode monitor viii)Watch Dog Timer. The protection relays if enabled will send signals to trip the breaker through 86G. Extreme conditions of operation or fault conditions are latched with a Hooter alarm to help the user to identify the cause for tripping of the excitation system. The parameters are also viewable via the front panel LCD display of the AVR unit. Password protection offers restrict access for changing the parameter setting. The oscillographic data recording feature can be used to record the generator voltage, current, frequency, kW, Power Factor, exciter field voltage and exciter field current. 1A+1M(Single Channel) – 1A+1M Digital AVR panels for brushless excitation systems are manufactured using Reivax make AVR's' depending on the exciter filed rating & features required by customer.