Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Patent
1992-09-21
1994-04-12
Wieder, Kenneth A.
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
323207, 323212, 322 20, H02J 324
Patent
active
053029062
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
In an electrical supply network containing generators, intermediate transient effects which lead to critical fluctuations in the real power can occur between the generators. To damp out this fluctuation in the real power, reactive power compensators are typically used. Reactive power compensators are also used to stabilize the voltage of the supply network. However, a measured variable providing information on the fluctuations in the real power is required to control such a reactive power compensator. Such a measured variable may be, for example, the load angle of a generator. However, this variable can be determined only indirectly from the generator itself. Therefore, other measured variables, for example, frequency signals, have been used to control the reactive power compensator. A circuit arrangement which uses frequency signals to control a reactive power compensator is disclosed in DE 2,851,871. However, even this measured variable is satisfactory only within limits, since the measured variable actually required is the frequency difference between the generator and the supply network, which once again cannot be measured directly.
DE AS 1,230,126 discloses a device which detects the load angle metrologically in the immediate or non-immediate vicinity of the generator using components which are dependent on the terminal voltage and terminal current. In this case, the synchronous reactance X.sub.d is predetermined. This device is concerned with regulating relatively slow static processes on site at the generator.
The present invention seeks to provide a method for determining the load angle of a generator in an electrical supply network from measured variables which are present locally on a line and a device for implementing that method.
SUMMARY OF THE INVENTION
The present invention achieves this by providing in a system including a generator connected to an electrical supply network via a line, a method including steps of: location in the supply network; power flow signal Q; supply network to determine equivalent variables for the generator and line parallel reactance component Y.sub.Q and for the generator and line series reactance component Y.sub.L ; ##EQU1## where Im denotes the imaginary part, Re denotes the real part and j denotes the complex operator, and Y.sub.Q and Y.sub.L are complex variables; of the load angle of the generator or of the fluctuations in the real power, to an indicating device.
In this way, an output signal .delta. which provides sufficiently accurate information on the magnitude of the load angle is made available. In this case, the method can be implemented at any location in a supply network. The computing device provided to solve the mathematical relationships can be designed as a computer or as an analog circuit.
Considering the transient generator reactance X.sub.d' for the series reactance component Y.sub.L is advantageous. The transient fluctuations in real power, which are of particular interest, are preferably determined by detecting a phase difference between the location of the measurement and the generator e.m.f.
Feeding the output signal .delta., as a regulating variable, to the regulating device of the reactive power compensator, the reactive power compensator being connected to the line is advantageous since fluctuations in real power in the network are effectively damped. The method of the present invention is particularly simple since the reactive power compensator does not need any additional measured variables from the generator. The measured variables at the location of the connection to the reactive power compensator to the line are adequate, the location of the connection being used as a reference node.
An additional generator can also be connected via an additional line to the supply network. Output signals 67a and 67b are initially formed in the computing device for each generator, and a difference signal .DELTA..delta. is formed therefrom. The difference signal .DELTA..delta. is supplied to the regulating device as a
REFERENCES:
patent: 4292580 (1981-09-01), Ott et al.
patent: 4412171 (1983-10-01), Kaufhold
patent: 4755738 (1988-07-01), Shimamura et al.
patent: 5134356 (1992-07-01), El-Sharkawi et al.
patent: 5187427 (1993-02-01), Erdman
IEEE Transactions on Power Apparatus and Systems, vol. PAS99, No. 1, Feb. 1980, New York, US, pp. 256-267; J. Meisel: Transient Stability Augmentation Using a Hierarchical Control Structure.
IEEE Transactions on Power Apparatus and Systems, vol. 103, No. 2, Feb. 1984, New York, US, pp. 265-274; B. Ooi et al.: Co-ordination of Static Var Compensation With Long Distance Radialtransmission System for Damping Improvement.
Siemens Aktiengesellschaft
Tobin Christopher
Wieder Kenneth A.
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