JPH0360334A - Reverse-tidal-current-proof device in cogeneration equipment - Google Patents

Abstract

PURPOSE:To prevent reverse tidal-current from being caused to the side of an utility system by absorbing the excess energy of a generator into a spare load for a fixed time when load current is suddenly reduced in the generation equipment using the generator having slow response to power command. CONSTITUTION:When constant load current fed from a generator and an utility system is suddenly reduced to I2 from I1, it is detected by a controller 1 that the situation of reverse tidal-current generation is generated from the current change of current transformers CT2, CT1, and a switch 3 is closed, and spare load current I3 for compensating load current reduced-component I1-I2 is permitted to flow. After this, by the controller 1, from the quantity of the load current I2, electric energy to be generated from the generator is computed, and power command is reduced to P2 from P1. When generator output is turned into P2 and is stabilized, then by the controller 1, the output of signal for disconnecting a spare load 2 is directed to the switch 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for preventing reverse power flow in a cogeneration system (hereinafter abbreviated as CGS) installed at an electric power consumer.

[Conventional technology] For consumers who consume a large amount of electricity, while receiving a constant supply of electricity from the electric power company, from the perspective of energy conservation, consumers independently operate rotating machines such as diesel engines, gas engines, and gas turbines. Llf of CGS, which generates electric power by installing a generator and rotating a generator, and effectively utilizes the exhaust heat from these rotating machines, has become popular.

Regarding the interconnection between CGS generators and the electric power company's power grid, necessary equipment measures have been taken to maintain safety in accordance with Grid Interconnection Technical Requirements Guidelines J. A specific example is shown in Figure 4. As shown in Figure 4, appropriate protection devices are installed to remove the failure and localize the failure area in the event of a failure within the CGS customer premises or a power system failure.In the figure, the DS is disconnected. , CBI, CB2 are circuit breakers,
ZCT is a zero-phase current detector, CT is a current detector, PT is a voltage detector, ○VGR is an overvoltage ground relay, 0CGR is an overvoltage ground relay, DSR is a short-circuit direction relay, OV
R is '14 voltage relay, UFR is underfrequency wI electric appliance,
UVR is an undervoltage relay, and 0CR-H is an overcurrent relay. In FIG. 4, solid line blocks represent $1 protection electrical appliances required for parallel connection with the grid, and each wave line block represents an example of an equipment protection relay.

A reverse power relay (RPR) shown in FIG. 4 is also one of the protection devices. This relay RPR detects when there is a power outage on the power grid side and the generator is left running alone, and the power from the generator flows out to the power grid side (this state is called reverse power flow). ! j2 is placed to release the machine from the grid.

[Problem to be solved by the invention] However, when a generator is connected to a power grid and a CGS is operated, a reverse power flow phenomenon occurs on the grid side due to load fluctuations, and even under normal operating conditions, A problem has arisen in which the INPR operates, opens the circuit breaker (CBI) at the interconnection point, cuts off the interconnection, and stops power transmission. This is originally an electric power system or CGS! Relays intended to prevent breakdowns and accidents within important premises are judged to be malfunctioning due to a similar phenomenon that occurs in the operation of electric power.

This problem can be solved by adjusting the output of the generator if load fluctuations are planned in advance, but if the load fluctuations are unpredictable or sudden, it is possible to deal with this problem by using the generator. Since it was impossible to do so and the above-mentioned problems occurred, some kind of preventive measure was desired.

The present invention has been made in view of such demands, and an object of the present invention is to prevent reverse power flow due to load fluctuations.

[Means for Solving the Problems] In order to achieve this object, the reverse power flow prevention device in the CGS of the present invention can be used in a cogeneration system interconnected with high-voltage general distribution lines, crystal pressure dedicated lines, and special high-voltage transmission lines. The present invention is characterized by comprising means for detecting a situation in which a reverse power flow occurs, and means for promptly applying a spare load to prevent the occurrence of a reverse power flow when such a situation is detected.

[Example] Hereinafter, the present invention will be specifically explained based on Examples.

Embodiment 1 FIG. 1 shows an example of a single line diagram when the present invention is applied to a CGS. However, in FIG. 1, descriptions of protective relays, etc. are omitted. In Figure ■, C
DI is a circuit breaker on the grid side, and CB2 is a circuit breaker on the generator side.

1 is the grid IT current (CT2), generator current (CT1〉,
Reverse ill by adjusting the load current (CT3) etc.
This control device has a function of detecting the state of current generation, a power command function of commanding the amount of power generated to the generator, and a function of generating a signal to open and close the switch 3. 2 is a preliminary load, and resistance, water resistance, etc. are used. Reference numeral 3 denotes a switch that supplies or cuts off power to the reserve load in accordance with opening/closing commands from the control device 1.

The operation of these devices will be explained according to the time chart shown in FIG. First, it is assumed that a constant load current is supplied from the generator and the grid (FIG. 3(a)). Under this condition, the load is 71ttJi! When CT suddenly changes from 11 to CT2, the control device detects the situation of this change and CT2. It is detected that a reverse rat is occurring from the CTI current change, etc., and the switch 33 is closed and the load current change l is detected.
Flow a preliminary load current to supplement l-I2 (Fig. 3(b)).

Thereafter, the control device 1 calculates the amount of power that the generator should generate from the amount of the load current 2, and decreases the power command from 1'1 to P2. When the power generation amount of the generator reaches P2 and stabilizes, the control device FIT determines that there is no situation where a reverse power flow is occurring and transmits No. 13 to the switch 3 to cut off the preliminary load.

Example 2 FIG. 3 shows Example 2. A reverse power flow detector 4 is provided as a means for detecting the occurrence of reverse power flow, and this signal and the load current are used as input signals for the control i1. In this case, consideration should be given to interference with the protective relay (RPR), and the RPR will be prevented from operating due to instantaneous reverse power flow.

[Effect of the invention] In this way, in a CGS that uses a generator that responds slowly to power commands, even if the load current fluctuates rapidly, the surplus energy of the generator can be absorbed by the load for a certain period of time. , it becomes possible to operate the CG S safely and stably without systematically transmitting power.

[Brief explanation of drawings]

Fig. 1 is a wiring diagram showing Embodiment 1 of the present invention, Fig. 2 is a time chart showing the operation of each part of Fig. 1, Fig. 3 is a wiring diagram showing Embodiment 2 of the invention, and Fig. 4 is a CGS. FIG. 2 is a wiring diagram showing a conventional example. 1: Control device 2: Preliminary load

Claims (1)

[Claims] 1. In a cogeneration system connected to high-voltage general distribution lines, high-voltage dedicated lines, and special high-voltage transmission lines, means to detect situations where reverse power flow occurs, and to promptly install backup loads when the above situation is detected. 1. A reverse power flow prevention device in a cogeneration system, comprising means for releasing a spare load when the condition is released, and means for commanding a generator to generate power.