This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-283910, filed Sep. 19, 2000; No. 2000-284173, filed Sep. 19, 2000; and No. 2001-076843, filed Mar. 16, 2001, the entire contents of all of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a line linkage protective device for electricity generation equipment to be linked to an alternating current power line through a breaker, being equipped with an inverter for converting direct current power into alternating current power. More particularly, the invention relates to a line linkage protective device for an electricity generation equipment in which the sole operation of the electricity generation equipment in line linkage can be assuredly and readily detected, on the electricity generation equipment side, and protected at a low cost, without having to provide an expensive transfer breakage apparatus.
2. Description of the Related Art
In general, a line linkage protective device for electricity generation equipment is used for a high voltage consumer to make line linkage between the private power generation apparatus and the alternating current power line. Now, private power generation apparatuses include, for example, garbage-powered turbines or co-generation system. In recent years, there is used a small sized gas turbine electricity generation apparatus which is designed to provide an output of several tens of kilowatts by revolving a generator at high speed with a gas turbine.
In the line linkage protective device of this kind, a transfer breakage apparatus is provided, to protect a private power generation apparatus, based on the signal from a substation. However, as the transfer breakage apparatus of this kind necessitates use of the apparatus at both the substation and the private power generation apparatus ends of the transfer means, and use of an exclusive transfer channel (communication line), it inevitably becomes very expensive.
Also, as described above, in the line linkage protective device of the power generation equipment of this kind, if the output power of the synchronous generator and the required power of the load are approximately equal to the effective portion and the ineffective portion, then neither the frequency nor the voltage shows changes even slightly. Accordingly, in such a case, continuous operational state is maintained, upon non-operation of any of the protective relays. This is the so-called phenomenon of xe2x80x9csole operationxe2x80x9d (islanding), which prevents re-closing of the breaker channel.
Conventionally, therefore, in order to prevent such islanding, there is adopted a method of applying transfer breakage to the breaker by providing an exclusive line from the substation. Such a transfer breakage apparatus opens the breaker by sending a break signal to the breaker on detecting a signal in which the breaker of a superior substation is opened.
However, as the transfer breakage apparatus of this kind is extremely costly to private power generation companies of medium and small capacities of several hundred kW, and further, as it is necessary to install transfer means and a transmission channel, it is not possible to obtain the merit of energy cost reduction by the laying of the private power generation apparatus.
An object of the present invention is to provide a line linkage protective device for an electricity generation equipment in which the sole operation of the electricity generation equipment in line linkage can be assuredly and readily detected on the electricity generation equipment side and protected, without providing an expensive transfer breakage apparatus.
The above object can be attained by the following inventions:
According to the first aspect of the present invention, there is provided a line linkage protective device of an electricity generation equipment equipped with an electric generator driven by a motor, and linked to an alternating current power line with an inverse current through a breaker, comprising a governor for controlling the frequency of the generator under an instruction signal from an external source, function generating means having a function characteristic of the frequency instruction for detecting the frequency variation rate of the generator and outputting a large output signal to the value of the frequency variation rate, effective power adjusting means for detecting the effective power of the generator and outputting the output signal proportionate to the detected signal, protective relay means for sensing abnormality of the frequency variation rate of the generator and outputting the breaking signal of the breaker, and an adder for synthesizing the output signal from the function generating means with the output signal from the effective power adjusting means and inputting the synthesized result to the governor as an instruction signal; wherein, at the time of a power outage on the alternating current power line side, the power outage on the alternating current power line side is detected by shifting the frequency variation rate of the generator to a level sensed by the protective relays by the function characteristic of the function generator.
By this step, there is used a signal made by synthesizing an output signal from the function generating means having a function characteristic of the frequency instruction for outputting a large output signal to the value of the variation rate of the frequency of the generator, with an output signal from the effective power adjusting means for outputting an output signal proportionate to the effective power of the generator, as an instruction signal of the governor for controlling the frequency of the generator. And, by shifting the frequency variation rate of the generator to a level which can be sensed by the protective relay means based on the function characteristic of the function generating means on a power supply outage on the alternating current power line, the power supply outage is detected. Furthermore, by shifting the slight frequency variations rate to the level sensed by the protective relay means, the islanding of the private power generation equipment in the line linkage is steadily and readily detected and protected on the private power generation equipment side at a low cost, without having to provide the expensive transfer breakage apparatus of the conventional case.
According to the second aspect of the present invention, there is provided a line linkage protective device for electricity generation equipment equipped with an inverter for converting direct current power into alternating current power, linked to an alternating current power line through a breaker, comprising frequency detecting means for detecting the output frequency of the inverter, frequency variation rate detecting means for detecting the variation rate of the frequency detected by the frequency detecting means, power factor reference judging means for defining by function the relationship between the frequency variation rate and the power factor so that the power factor reference for promoting the variation of the frequency is outputted respectively to the inverter by varying the power factor of the inverter to the direction of advance when the frequency variation rate is positive and by varying the power factor of the inverter to the direction of delay when the frequency variation rate is negative, based on the frequency variation rate detected by the frequency variation rate detecting means, and protective means for detecting the frequency variation promoted according to the variation of the power factor of the inverter formed by giving the power factor reference outputted from the power factor reference judging means to the inverter, and opening the breaker to release the private power generation equipment from the alternating current power line.
By this step, the variation rate of the output frequency of the inverter is detected. And, when the frequency variation rate is positive, the power factor of the inverter is caused to vary in the direction of advance, and when the frequency variation rate is negative, the power factor reference for promoting the variation of the frequency is given to the inverter respectively by varying the power of the inverter in the direction of delay. In this manner, by varying the power factor of the inverter, the frequency variation can be enlarged. Accordingly, the islanding of the private power generation equipment in the line linkage is steadily and readily detected and protected on the private power generation equipment side at a low cost, without providing an expensive transfer breakage apparatus as required in the conventional case.
According to the third aspect of the present invention, the device comprises the frequency detection means equipped with a synchronous generator driven by a motor, for detecting the frequency from the output of the synchronous generator of the private power generation equipment linked to the alternating current power line through the breaker, voltage variation detecting means having the output voltage of the alternating current power line as an input, for eliminating errors in the frequency generated by the voltage variation by locking the output from the frequency detection means when the input voltage varies, frequency variation rate detection means for detecting the variation rate of the frequency outputted from the voltage variation detecting means, voltage swinging signal generating means for operating the voltage swinging signal in a manner to promote the variation of frequency, based on the frequency variation rate detected by the frequency variation rate detection means, and giving the voltage swinging signal to the automatic voltage adjuster of the synchronous generator, and protecting means for detecting the frequency variation promoted by the voltage variation of the synchronous generator formed by giving the voltage swinging signal operated by the swinging signal generating means to the automatic voltage adjuster and opening the breaker to release the synchronous generator from the alternating current power line.
By this step, the variation rate of the frequency of the synchronous generator of the private power generation equipment is detected. And, when the frequency variation rate is positive, the voltage of the synchronous generator is caused to vary in the lowering direction, and when the frequency variation rate is negative, the voltage of the synchronous generator is caused to vary in the raising direction, to enlarge the frequency variation. Consequently, the islanding of the private power generation equipment in the line linkage is steadily and readily detected and protected on the private power generation equipment side, without providing an expensive transfer breakage apparatus as required in the conventional case.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.