56 results about "Synchronous generator excitation" patented technology

An exciter system for the field of a synchronous generator excitation is provided. The exciter system includes an AC power source; a three-phase thyristor bridge having six legs, the three-phase bridge being connectable with the AC power source, and being adapted to provide a variable DC voltage output; a thyristor in each of the six legs of the three-phase bridge, wherein the thyristors provide a path for a device current; and a three-phase AC line filter series, including series resistive and capacitive elements across each phase of the AC power source and a plurality of bleed resistors, wherein at least one bleed resistor is connected to each AC input connection of the filter.

The invention discloses an excitation system simulation test device for a synchronous generator. The device comprises a main control module, an analogue signal measurement module, a switching value input module, a simulation signal output module, a switching value output module, a communication interface module and an upper computer terminal, wherein the main control module realizes control coordination and data processing; the analogue signal measurement module realizes conditioning, isolation, filtration and measurement of an input analogue signal; the switching value input module realizes the conditioning and isolation of an input switching value signal; the simulation signal output module realizes the conditioning, isolation, filtration and power amplification of a simulation result signal; the switching value output module realizes the conditioning and isolation of an output switching value signal; the communication interface module is used for realizing data interaction; and the upper computer terminal is used for sending a control instruction and experimental parameters, receiving simulation result data simultaneously, and recording and displaying the simulation result data on a terminal interface.

The invention belongs to the technical field of automation control of ships and the technical field of generator control of ship electric power systems, in particular relates to an excitation control device of a synchronous generator for ships. The device comprises an excitation control mainboard, a human-computer interface and a switching power supply, wherein the excitation control mainboard comprises a CPU main control unit, a data acquisition circuit, an A / D conversion circuit, a real-time calendar clock circuit, a watchdog circuit, a rectifying circuit, an MOSFET driving circuit, a de-excitation circuit, an on-off input circuit, a communication interface circuit and an LCD driving circuit; and the human-computer interface comprises keys, an LCD display and an LED indicating lamp. The invention has the advantages of flexible and convenient installation and use, high measuring accuracy, high execution speed and stable operation, and has the functions of monitoring and controlling the terminal voltage of the synchronous generator in real time, regulating the allocation of the reactive power of the synchronous generator in real time and improving the stability of parallel operation of the synchronous generator. The human-computer interface is abundant, and a CAN communication interface and an upper computer are used for exchanging data. The invention is designed according to the standards of a ship power station and can be widely applied to an automatic control system of a generator set in the ship power station.

In order to solve the problems in the modeling process of an existing excitation system that a measurement safety requirement is high and test work load is large due to the fact that a traditional method for measuring a transient time-constant of a generator stator open circuit generally requires changing a circuit wiring for one time, a method for measuring the stator open circuit transient time-constant of a synchronous generator is provided. According to the method, a generator no-load simulation system is established based on a matlab / simulink platform, practically measured exciting voltage of a synchronous generator serves as input, a generator output voltage curve is simulated and obtained, a practically measured curve and the simulation curve of the output voltage of the generator are compared, and the transient time-constant of the synchronous generator stator open circuit is obtained through fitting. The measurement method combining a test and simulation fitting, the problems of complex wiring and low result accuracy of the traditional test method are effectively solved, and high economy and practical value are achieved.

The invention discloses a proportional-integral-differential (PID) prediction function-based excitation control method, which is used for an excitation control system for a synchronous generator. By combining characteristics of PID and prediction function control, a PID form-based prediction function controlled target function is provided, and the optimized controlled quantity is obtained by optimized calculation, and is taken as a control end input signal of a silicon controlled (or a full-control device) in the excitation control system so as to control the excitation current of the synchronous generator and further influence the terminal voltage thereof. An excitation controller acquired by the method has structural characteristics of proportion, integral and differential in a broad sense, has respective advantages of the PID and the prediction function control, and is convenient to implement. The method overcomes the defects that the conventional prediction control method has high on-line calculated amount and the PID control method has a limited regulating range, and is a novel and effective control strategy for stabilizing a power system.

The invention relates to a wind power generating technology and discloses a speed-self-regulating synchronous generating system. The speed-self-regulating synchronous generating system is characterized by comprising a shell and an exciter which is coaxially connected with the left side of the shell, wherein an electromagnetic torque coupler and a synchronous generator sleeved on the outer side of the electromagnetic torque coupler are arranged inside the shell; the electromagnetic torque coupler comprises an inner rotor shaft and an outer rotor shaft; an inner rotor is connected onto the inner rotor shaft; an outer rotor is connected onto the inner side of the outer rotor shaft; the synchronous generator comprises a generator rotor and a generator stator; the generator rotor is fixed on the outer side of the outer rotor shaft; and the generator stator is fixed inside the shell. The rotor of the synchronous generator is integrated with the outer rotor of the variable-frequency speed-regulating electromagnetic torque coupler, so that the rotation speed of the rotor of the synchronous generator is a synchronous rotation speed; and the exciting current is changed by regulating input of the synchronous generator exciter so as to ensure that the output voltage and the frequency of the generator are constant.

The invention discloses a parameter identification method of a synchronous generator excitation system, which is used for outputting an optimal solution of a parameter Theta of the synchronous generator excitation system. The parameter identification method comprises the following steps of building an excitation system simulation module M; determining an equivalent standard J; and carrying out disturbance test on the excitation system with a signal X, and acquiring each real response index Y<Ri>. The parameter identification method also comprises the following steps of determining weight W corresponding to the Y<Ri>, wherein Sigma W is equal to 1; selecting a value of the parameter Theta, substituting the value of the parameter Theta into the M, carrying out disturbance test on the M with the signal X, and acquiring each real response index Y<Ii>; calculating an error e between the Y<Ii> and the Y<Ri>, and calculating a weight value e<W> of the error e if the error e conforms to the equivalent standard J; and taking the value of the parameter Theta as the optimal solution to be output if the e<W> is the minimum e<Wmin>, wherein the numbers of the Y<Ri> and the Y<Ii> are both N, and i is equal to 1, 2 until N. By the parameter identification method, the optimal solution can be found out from a parameter solution cluster of the synchronous generator excitation system, and the identification speed is increased within an acceptable precision range to the great extent.

The present invention provides a virtual synchronous generator controller without using current feedback. The virtual synchronous generator controller comprises the following parts of: 1) a rotor motion equation: a virtual rotor angular frequency and phase are obtained through calculation, and the virtual rotor angular frequency is adopted as the angular frequency of an inverter; 2) voltage control: synchronous generator excitation control and reactive voltage drop characteristics are simulated to control the output voltage amplitude of the inverter; 3) an inverter output power calculation equation: a power transmission line transmission power calculation method is adopted to calculate the reactive power and virtual electromagnetic torque of the inverter, wherein the inverter output power calculation equation is characterized in that calculation can be performed with no current quantity required; and 4) a dq transformation unit and a dq inverse transformation unit: and the angular frequency and phase of the rotor motion equation are adopted as a reference phase angle. The above parts are integrated so as to form the virtual synchronous generator controller without using current feedback. Compared with existing methods, the virtual synchronous generator controller without using current feedback of the present invention does not need current feedback, so that a control algorithm can be simplified; and a current sensor is omitted, and the construction cost of the inverter can be reduced.

The invention discloses a PSS (Power System Stabilizer) switching based synchronous generator excitation control method. A synchronous generator comprises a prime motor, a generator and an excitation regulator, wherein the excitation regulator is provided with a power system stabilizer; the control method comprises the steps of: step 1, setting a soft switch module in a PSS model of the power system stabilizer to enable the power system stabilizer to be switched between a PSS1A model and a PSS2A / PSS2B model; step 2, detecting an on / off state of a power adjusting joint of the prime motor in real time; step 3, controlling the soft switch module based on the on / off state to enable the soft switch module to be switched off and enable the power system stabilizer to run according to the PSS1A model when the power adjusting joint is in an off state, and enable the soft switch module to be switched on and enable the power system stabilizer to run according to the PSS2A / PSS2B model when the power adjusting joint is in the on state. The PSS switching based synchronous generator excitation control method has the advantages of PSS1A and PSS2A / PSS2B.

A method for modeling an excitation system for a synchronous electrical power generator including: selecting a standard mathematical excitation system model from a plurality of standard excitation system models stored electronically; wherein the selected standard model is selected based on a similarity to the excitation system and can be an IEEE standard model; collecting data from the excitation system; determining parameter settings for the selected standard model using first pre-calculated and then collected (measured) data; verifying the selected standard model with tailored parameter settings by comparing an output of the model to a corresponding output of the excitation system; storing electronically the verified selected standard model with tailored settings; generating a report of the verified selected standard model with the tailored settings; performing rapidly and automatically model generation from a maintenance computer proximate to the excitation system; performing rapidly and automatically model generation without the need for system experts or extra equipment; and providing means to repeat test an operating excitation system at low cost and risk

The invention discloses a synchronous generator parameter identification and control method based on a WAMS. An improved saturated cutset algorithm is adopted in a communication network framework of the WAMS, a method based on time domain transformation is adopted in parameter identification of a synchronous generator, and excitation backstepping control based on a neural network is adopted in control over the synchronous generator. The improved saturated cutset algorithm of the communication network framework of the WAMS, synchronous generator parameter identification of the method based on time domain transformation and the synchronous generator excitation backstepping control method based on the neural network are combined together, and therefore the system has euryzonal performance, intellectuality and reliability.

The invention relates to a synchronous generator excitation system model parameter identification optimization method. The method comprises the following steps: 1) carrying out no-load step response test on a synchronous generator excitation system to obtain a test output signal; 2) constructing an excitation system simulation model, and determining per-unit guide rule constraints; 3) modifying system model parameters of the simulation model; 4) applying an excitation signal same with that of the test to the simulation model to obtain a simulation output signal; 5) calculating per-unit error of each performance index of the test output signal and the simulation output signal, and judging whether the per-unit error of each performance index meets the per-unit guide rule constraints respectively, and if so, carrying out the step 6), or otherwise, returning to the step 3); and 6)carrying out optimization on the system model parameters according to the per-unit error of each performance index to obtain optimized optimal model parameters and outputting the model parameters. Compared with the prior art, the method facilities obtaining the optimum model parameters of the excitation system.

The invention discloses a closed-loop testing system and a closed-loop testing method for an excitation and packet switching system (PSS) control device of a synchronous generator. The closed-loop testing system comprises a real-time simulation work station, a real time digital system (RTDS), an analog output board card, a power amplifier, an excitation and PSS control device and a digital output board card, wherein the real-time simulation work station is connected with the RTDS; the RTDS transmits current and voltage signals to the excitation and PSS control device through the analog output board card and the power amplifier; the RTDS transmits a grid-connected circuit breaker switching signal of the synchronous generator to the excitation and PSS control device through the digital output board card; and the excitation and PSS control device transmits a pulse trigger signal of a six-pulse rectifier bridge to the RTDS through the digital output board card. The self-parallel excitation closed-loop testing system for the excitation and PSS control device of the synchronous generator is flexible in testing and can perform multiple types of tests.

The invention discloses a semi-physical simulation technology-based synchronous generator excitation test training system. According to the system, a virtual simulation technology is imported into excitation system closed-loop test of synchronous generators; a virtual synchronous generator excitation system module, a power driving device and a multifunction electric parameter tester are connectedinto a whole; and a real-time virtual synchronous generator excitation system is used for testing tested systems, is connected with the power driving device through an I / O interface, transfers signalsto the tester to carry out reading, and can be connected with an upper computer through a communication interface so as to display excitation test operation conditions and carry out efficient and hardware-in-loop virtual simulation. The synchronous generator excitation system module is used for simulating operations of real excitation systems; the power driving module is used for acquiring and amplifying signals; the multifunctional electric parameter test is used for correctly detecting required data indexes to provide reference basis; and the upper computer is used for realizing a visual function of the system. The system provided by the invention is capable of solving the defects that the physical test is inconvenient to operate, tedious in project and relatively long in period, enriching the test contents, enabling learners to grasp detailed principles of excitation test more rapidly and being put into practical production and application more rapidly.

The invention discloses a synchronous generator excitation system based on fuzzy PID control and a voltage regulation method. The method comprises the following steps: calculating the total generator-end voltage of a synchronous generator according to a sampled generator-end voltage; calculating a voltage deviation and a voltage deviation differential according to a reference voltage and the totalgenerator-end voltage, determining fuzzy control parameters according to the voltage deviation and the voltage deviation differential, and carrying out PID regulation of a voltage loop on a regulating point according to the fuzzy control parameters and the reference voltage, and obtaining a reference value of the excitation voltage, wherein the fuzzy control parameters comprise a proportional parameter P, an integral parameter I and a differential parameter D; regulating a current loop according to the detected excitation voltage of the generator and the given reference value of the excitation voltage, and outputting an adjusted excitation voltage; carrying out PWM waveform modulation on the adjusted excitation voltage to obtain a PWM wave signal; and outputting the PWM wave signal to a driving circuit to drive an IGBT to be switched on. The technical problem of generator excitation current / voltage overshoot due to the adoption of traditional PID regulation control in an existing synchronous generator excitation system is solved.

The invention relates to a double permanent magnet power-frequency brushless synchronous generator. A composite stator, a permanent magnet rotor and a compensating rotor are arranged inside a power generator body, wherein the permanent magnet rotor and the compensating rotor are arranged at the lower end of the composite stator, the rear ends of the composite stator and the compensating rotor are provided with a permanent magnet exciter assembly and a signal sensor assembly, the lower ends of the permanent magnet exciter assembly and the signal sensor assembly are also respectively provided with a rotary AVR (Automatic Voltage Regulator), the permanent magnet exciter assembly comprises a permanent magnet exciter stator and a permanent magnet exciter rotor, and the signal sensor assembly comprises a signal sensor stator and a signal sensor rotor. According to the invention, by adopting a forward / reverse series compensation technology, the adaptability of power factor of the generator is improved; the defects of uncontrollable excitation and nonadjustable voltage of the traditional permanent magnet power-frequency brushless synchronous generator can be overcome by using the rotary AVRs, and the voltage adjusting level is improved; by adopting a permanent magnet excitation technology, compared with the electric excitation power-frequency brushless synchronous generator, the double permanent magnet power-frequency brushless synchronous generator has the advantages that the efficiency of the double permanent magnet power-frequency brushless synchronous generator can be improved by 4-8 percent, the size and the weight can be reduced by 30-40 percent, and the copper and iron consumables can be saved by about 20-30 percent.

An exciter system for the field of a synchronous generator excitation is provided. The exciter system includes an AC power source; a three-phase thyristor bridge having six legs, the three-phase bridge being connectable with the AC power source, and being adapted to provide a variable DC voltage output; a thyristor in each of the six legs of the three-phase bridge, wherein the thyristors provide a path for a device current; and a three-phase AC line filter series, including series resistive and capacitive elements across each phase of the AC power source and a plurality of bleed resistors, wherein at least one bleed resistor is connected to each AC input connection of the filter.

The invention provides a tuning method for a difference coefficient of a synchronous generator excitation system. The method comprises the following steps: firstly, clearly distinguishing the number of regional central points, an operating voltage of each central point in each period, the number of generator nodes, active output power of each generator, and a load value of power supply by each generator; then, calculating a standard deviation index of a central point voltage, measuring voltage fluctuation, calculating an average active power grid loss rate index, and considering the operationeconomy of the system; and finally, establishing a multi-objective optimization model of the difference coefficient of the synchronous generator excitation system, taking the minimum of the standard deviation of the central point voltage and the average active power grid loss rate as an objective, and calculating an optimal difference coefficient by considering constraint conditions such as powerflow constraint, control variable constraint and safety constraint. According to the tuning method for the difference coefficient of the synchronous generator excitation system, grid voltage can be effectively improved and power grid loss can be effectively reduced.

The invention discloses an offline temperature characteristic detection method for a SiC (Silicon Carbide) deexcitation resistor, belonging to the detection technology of SiC deexcitation resistors of synchronous generator excitation systems. The offline detection method is characterized by comprising the following steps of: connecting the SiC deexcitation resistor and a testing power supply according to a predetermined time length T; and meanwhile, monitoring the current, the voltage and the surface temperature value of the SiC deexcitation resistor by using an ammeter, a voltmeter and a thermodetector to obtain the temperature characteristic of the SiC deexcitation resistor, wherein the predetermined time length T for switching on the power supply is determined according to 20-50 percent of rated energy of the SiC deexcitation resistor. Aiming at the present circumstance that the complex online deexcitation testing detection method for the generator is adopted for the temperature characteristic of the SiC deexcitation resistor in China, the invention provides a new detection method which is economical and practical as well as safe and simple. Therefore, the SiC deexcitation resistor with defects can be found, the running deexcitation resistor is ensured in the sound condition, and the safety and the reliability of an excitation device and the generator are improved.

The invention relates to a performing evaluation method of a synchronous generator exciting system. The method comprises the following steps: (1) building a tree-like evaluation model of the synchronous generator exciting system, wherein the top layer of the model is the synchronous generator exciting system performance to be evaluated; the bottom layer includes a plurality of basic evaluation factors; the middle is provided with at least one layer, and each layer includes a plurality of classified evaluation factors; (2) determining the weights of all basic evaluation factors and the classified evaluation factors; (3) obtaining the basic evaluation results of all basic evaluation factors at the bottom layer; and (4) calculating from the bottom layer of the tree-like evaluation model by layers according to the basic evaluation result and the weight of each evaluation factor so as to obtain the overall evaluation result of the synchronous generator exciting system performance to be evaluated on the top layer. Compared with the prior art, the method has the advantages that the performances of the exciting system can be accurately, stably and conveniently evaluated, so that complete, reliable and timely basis can be provided to the electric power system dispatching; and the method is of important theory and practice significance to the guiding of the site work and the parameter optimizing.

The invention discloses a design method of a synchronous generator excitation output feedback controller. First, a three-phase state space system model of a synchronous generator is built; then, the three-phase state space system model is reshaped equivalently into a four-phase state space system model by using a variable replacement method; then, an excitation controller is designed through output feedback; and finally, an optimized excitation controller is obtained by using a quadratic sum method. The existing excitation control algorithm is complex and state feedback cannot be realized in a power system. The method solves the problems in the prior art.

The invention discloses a secondary development method of a synchronous generator excitation regulator control program integrated embedded language, comprising the steps as follows: (1) compiling an embedded script program using lua scripting language; (2) modifying the running environment program of the script program according to an operating system and a compiler used so as to link the running environment of the script program to a host program in the form of program library, wherein the host program is an excitation regulator C language control program; (3) writing an interface function for calling the script program from the host program and an interface function for accessing the host program from the script program; and (4) initializing the running environment and the running state of the script program, and completing registration of the interface function for calling the script program from the host program in the host program so as to enable the host program to read, compile and execute the script program by calling the interface function of the script program.

The invention discloses a distributed-type inertial brushless excitation synchronous power generator. The distributed-type inertial brushless excitation synchronous power generator comprises a generator base, a rotating shaft, a junction box and an inertial-distributed-type rotor assembly, the inertial-distributed-type rotor assembly sleeve the rotating shaft, the rotating shaft penetrates throughthe generator base in the left-right direction, the rotating shaft and the inertial-distributed-type rotor assembly are integrated in the generator base, and the junction box is arranged outside thegenerator base; and the inertial-distributed-type rotor assembly comprises a fan, a first auxiliary flywheel, a synchronous power generator excitator, a rotary rectifier disc, an excitation power generator armature and a second auxiliary flywheel. The large distributed-type inertia of the power generator is utilized for energy storage under the special environments such as interference electricityand flickering of a power source, mechanical energy is converted to electric energy, short-time voltage leap is compensated, reliable supplying with the continuous output voltage and stable frequencyof the power generator is achieved through automatic loading, and the reliability problem of an emergency power supply system is solved.

The invention relates to a method of acquiring basic evaluation data of synchronous generator excitation system performance. The method of acquiring basic evaluation data of synchronous generator excitation system performance includes the steps: determining the basic evaluation factors of synchronous generator excitation system performance; determining the acquisition channel of the basic evaluation data corresponding to the basic evaluation factors; and finally acquiring the basic evaluation data through the acquisition channel. The determined basic evaluation factors not only include a sensitive basic evaluation factor, but also include an insensitive basic evaluation factor, so that the comprehensiveness of the evaluation data is improved; and the determined acquisition channel includes field tests, simulation calculating of excitation system, nameplate technology parameter data and power grid operation record data, and performs adaptive selection for different basic evaluation factors, so that accuracy of the evaluation data is improved. The method of acquiring basic evaluation data of synchronous generator excitation system performance can acquire comprehensive and accurate evaluation data so as to provide basis for graded evaluation of excitation system performance.

A synchronous generator de-excitation circuit based on a thermistor comprises a generator rectification circuit, a magnetic field breaker and a synchronous generator excitation winding, wherein the synchronous generator excitation winding is further connected with the de-excitation circuit in parallel. The de-excitation circuit comprises a thermistor and a nonlinear field suppression resistor, wherein the thermistor and the nonlinear field suppression resistor are connected in series. The thermistor (PTC) with positive temperature characteristics is selected as a closed switch of a de-excitation circuit. The de-excitation circuit solves the problems of high manufacturing cost, complex control loop, low reliability and the like of a de-excitation device in the traditional de-excitation method of the synchronous generator, is one of important safeguard measures for safe and stable operation of the synchronous generator, and has important practical significance for power generation engineering in China.

The present invention discloses a synchronous generator excitation control method based on a fuzzy sliding mode. The method comprises: the step 1, establishing each unit simplification model and a fuzzy sliding mode controller model of a synchronous generator excitation system; the step 2: taking the error e1 of the feedback voltage U and the given voltage U0 at the end of a synchronous generator as the input of a sliding mode variable structure control portion, and taking the e1 and the (img file='DDA0001336670490000011. TIF' wi='36' he='63' / ) as the input of a fuzzy control portion; the step 3: obtaining an excitation voltage Uf after overlapping of the fuzzy control output us and a sliding mode variable structure; the step 4: obtaining the excitation voltage UF of the synchronous generator through processing the feedback voltage U by employing a power amplification unit; and the step 5, taking the UF as the input of the synchronous generator unit, and obtaining the actual output voltage UG of the synchronous generator, wherein the actual output voltage UG of the synchronous generator is taken as the input of the voltage measurement unit to obtain the feedback voltage U at the end of the synchronous generator. The synchronous generator excitation control method based on the fuzzy sliding mode ensures the excellent static and dynamic response capability of the generator system.

The invention discloses a dynamic simulation test device and test method for a static variable-frequency starting system of a gas turbine generator. The device comprises a synchronous motor-generatorset, a static variable-frequency starting system, a voltage source type frequency converter system, a synchronous generator excitation system, an automatic quasi-synchronization device and a load resistance box; the input end of the synchronous motor-generator set is connected with the output end of the voltage source type frequency converter system; the output ends of the synchronous motor-generator set, the static variable-frequency starting system, the synchronous generator excitation system and the automatic quasi-synchronization device are connected with the load resistance box; the inputends of the static variable-frequency starting system, the voltage source type frequency converter system, the synchronous generator excitation system and the automatic quasi-synchronization device are connected with an alternating current power supply. The test device and method have the advantages that the problem that a gas turbine generator static variable-frequency starting dynamic simulation test device and method are lacked in the prior art is solved, and testing and simulation are conducted through the dynamic simulation test device.

The invention provides a thermal power plant SG excitation system optimal parameter setting method based on an ACS algorithm. The method comprises the following specific implementation steps: firstly,building an SG optimization model; secondly, inputting a frequency deviation caused by a power grid fault into an excitation system configured with a PSS, and outputting an excitation voltage ufd after adjustment; and finally, feeding the ufd back to the SG, and carrying out next iteration, wherein a PSS parameter and an excitation gain parameter are set by adopting the ACS algorithm. And the above process is continuously circulated till that the algorithm converges to obtain the optimal setting parameter. The ACS algorithm effectively solves a problem that the PSS parameter and the excitation gain parameter of the thermal power plant SG are difficult to set optimally in a practical application. The method has the following two advantages that firstly, a self-adaptive sequence based on anexploration direction is introduced into the algorithmso that a global search capability is remarkably improved, and the PSS parameter and the excitation gain parameter are prevented from falling into local optimum; and secondly, the ACS algorithm adopts a single-agent search mechanismso that the algorithm can approach the optimal PSS parameter and the excitation gain parameter at a higher speedand higher convergence stability;

The invention discloses a generating device of synchronous generator exciting system identification signals which comprises a power unit (7), a signal generating unit (8) and a control unit (9); the power unit provides the needed working power for the other two units; the signal generating unit is connected with the generator terminal three-phase voltage and a neutral point respectively, and stacks the identification signal needed by an exciting system mould identification test to the voltage signal on the end of the generator according to the control signal provided by the control unit, the exciting system connected with four integrated signals which are respectively overlapped with the identification signal is connected into an input port; the control unit is used for generating a pseudo-random or a step signal which is provided to the signal production unit, or outputs directly from an output signal port. The invention provides a new test device for the power system which not only solves the difficulty in doing the exciting system mould identification test for the generator without an extra-added signal input port, but also simplifies the test equipment, and improves the test efficiency.

The present invention relates to a unit comprising a plurality of varistors, specifically for the purposes of overvoltage protection in synchronous generator exciter discharge systems. Compared with existing varistor units, the unit of the invention is able to be transported more efficiently, is more compact, and requires fewer individual varistor units to be placed in a synchronous generator exciter discharge system while still achieving the required thermal and electrical ratings to perform to the desired requirements.