CN105098757A - Method for eliminating resonance of power distribution station - Google Patents

Abstract

The present invention relates to a method for eliminating resonance of a power distribution station, and a first resonance elimination device and a second resonance elimination device cooperate mutually for using. The method includes the steps as follows: 1) determining system parameters Omega C and Omega L, and determining a model of a computer resonance elimination device; 2) selecting a damping resistance value according to a neutral point serial resistance R0>=0.056 Omega L, and setting a resonance elimination value according to an open delta connecting damping resistance Rdelta<=0.32 Ohm; 3) completing an installation of the neutral point resistance, and completing an installation of the computer resonance elimination device. According to the method, the mutual cooperation of the first resonance elimination device and the second resonance elimination device has a complementary advantage, reduces a dead zone due to only one resonance elimination method, improves a reliability and a coverage area of resonance elimination without an obviously increased cost, and does no influence on a power grid at implementing. The method can be widely applied and popularized.

Description

A kind of harmonic elimination method of power distribution station

Technical field

The invention belongs to distribution technical field, especially a kind of harmonic elimination method of power distribution station.

Background technology

Due in 10kV isolated neutral system, electromagnetic potential transformer (PT) on bus needs usually by neutral ground, occur close unloaded bus, single-phase earthing disappear or system loading acute variation time, the nonlinear characteristic of PT magnetizing inductance will form parameter matching with system direct-to-ground capacitance, thus cause ferro resonance phenomenon, cause the overcurrent in system overvoltage and PT.Not only may cause PT high-voltage wire iron-melting fusing, PT burns or explodes, and even also there will be Explosion of on Arrester, weak insulation flashover, and the faults such as line-selected earthing device malfunction, have had a strong impact on the safe operation of system.

In order to prevent the generation of ferro resonance as far as possible, in recent decades, domestic and international expert has done large quantifier elimination and analysis of experiments, propose a lot of safeguard procedures, comprise: be installed in the microcomputer harmonic elimination device (also claiming secondary resonance eliminator) on the open-triangular winding of PT, a non-linear harmonic elimination electricity group is serially connected with a harmonic elimination damper between voltage transformer primary side neutral point and ground, adopt resonance elimination voltage transformer etc.About the research of above-mentioned various suppression measures is still not deep enough so far, especially lack and the Comprehensive of various suppression measures is compared, also comprehensive not to some important suppression measures and main in-problem understanding thereof, also there is doubt in many aspects in actual applications.

A harmonic elimination damper is serially connected with between voltage transformer primary side neutral point and ground by a non-linear harmonic elimination resistance R0, and it adopts neutral point damping resistance to eliminate resonance.When electrical network normally runs, on resonance eliminator, voltage <500V, R0 are high resistance (can reach hundreds of k Ω), and damping action is large, and resonance is not easily developed at initial period; When electrical network generation single-phase earthing, voltage higher (in 10kV electrical network its value about 1.7-1.8kV) on resonance eliminator, R0 is low value (tens k Ω), can meet the insulating monitoring requirement that PT open delta voltage is not less than 80V, and still can damped harmonic oscillation; When electrical network generation arc grounding, R0 still can keep certain resistance, and restriction instrument transformer shoves.

This device has to be eliminated the saturated resonance of PT and restriction and to shove two kinds of functions, but there is limitation in the application: 1) can only limit this PT and resonance not occur, to other PT in electrical network invalid (only effective one to one); 2) when there is single phase ground fault, the measured value of PT residual voltage has error, is therefore not suitable for being used in residual voltage amplitude and the higher occasion of angle precision requirement; 3) thermal capacity of device self is limited, even if the indirect arc grounding surge selecting thermal capacity relatively large excites down, and still can damage device.

Microcomputer harmonic elimination device also claims secondary resonance eliminator, is installed on the open-triangular winding of PT.Normal operation or generation single phase ground fault timer are failure to actuate, and once judge electrical network generation ferro resonance, positive and negative two thyristor ACs being connected in parallel on open delta two ends can be made to replace zero cross fired conducting with restriction and damping ferro resonance, after resonance is eliminated, thyristor ends voluntarily, if desired can repetitive operation.During device starts harmonic elimination, the full conducting of thyristor, in low resistance state, resistance is a few m Ω to tens m Ω.So little resistance value is enough to damping high frequency, fundamental frequency and frequency division 3 kinds of resonance, and effective to whole electrical network, and 1 instrument transformer namely only need be selected in a system to install harmonic elimination apparatus.

The major defect of microcomputer harmonic elimination device is difficult to correctly distinguish first-harmonic resonance and single-phase earthing.At present, the main distinction of first-harmonic resonance and single phase ground fault criterion is to the height of residual voltage U0.Usually, fundamental resonance is decided to be as U0 >=150V; Single phase ground fault is decided to be as 30V≤U0<145V.In order to prevent the situation of burning because error action of device makes the long-time overload of PT when single-phase earthing from occurring, usually must be higher by the criterion constant-voltage of this device fundamental resonance.Like this, under the clear condition that power frequency displacement voltage is not very high, (as aircraft carrier line closes a floodgate) device cannot action, just may make that some excitation property is not good enough, the fuse failure of the easy saturated PT of iron core.And this device is when power-to-ground capacitance is larger, it causes the accident of fuse failure helpless to preventing intermittent ground connection or ground connection disappearance moment instrument transformer because of instantaneous saturated shoving.In addition, under long-term indirect arc overvoltage excites, the electric current flowing through PT high pressure winding will enlarge markedly, and still may burn out PT.

Summary of the invention

The object of the invention is to propose a kind of comprehensive power distribution station harmonic elimination method, a harmonic elimination in power distribution station is combined with secondary harmonic elimination method, expand the sphere of action of harmonic elimination method, ensure that power distribution station is under the various operating modes of actual motion, more effectively can avoid the generation producing ferro resonance phenomenon, improve operation of power networks reliability, promote power distribution station operation level, ensure the safe operation of power distribution station.

The technical scheme that technical solution problem of the present invention adopts is:

A harmonic elimination method for power distribution station, both a harmonic elimination apparatus and secondary resonance elimination device are used in conjunction with each other, step is as follows:

(1) certainty annuity parameter ω C, ω L, determines microcomputer harmonic elimination device model;

(2) select damping resistance value according to neutral point crosstalk resistance R0 >=0.056 ω L, meet damping resistance R Δ≤0.32 Ω according to open delta and to adjust harmonic elimination resistance value;

(3) complete neutral resistor to install, complete microcomputer harmonic elimination device and install.

Advantage of the present invention and good effect are:

Both a harmonic elimination apparatus and secondary resonance elimination device are used in conjunction with each other by the present invention, have complementary advantages, decrease the blind area that a kind of harmonic elimination mode of single employing causes, improve reliability and the coverage of harmonic elimination, but cost does not increase significantly, can not impact electrical network during enforcement, can well be applied and promote.

Accompanying drawing explanation

Fig. 1 is the flow chart of this method.

Embodiment

Below in conjunction with accompanying drawing, also by specific embodiment, the invention will be further described, and following examples are descriptive, are not determinate, can not limit protection scope of the present invention with this.

As shown in Figure 1, implementation step is as follows for this harmonic elimination method handling process:

(1) according to R ₀>=0.056 ω L Selecting All Parameters: at normal operating voltage and not additional R ₀time, during 1/ ω C/ ω L=0.025 ~ 0.280, there is Subharmonic Resonance, during 1/ ω C/ ω L=0.180 ~ 0.680, first-harmonic resonance occurs.Along with R ₀increase, resonance range reduce, work as R ₀after being greater than a certain critical value, resonance range disappears, and namely resonance does not occur.Work as R ₀all first-harmonics and subharmonic can be eliminated during>=0.056 ω L.So according to R ₀>=0.056 ω L Selecting All Parameters.

(2) choose R according to system parameters ₀in-site installation is carried out after value.

(3), in the network of isolated neutral system, in order to reliably harmonic elimination, given critical point is:

$R_{\mathrm{\&Delta;}}=\frac{3\sqrt{X_L{X}_C\&CenterDot;n}}{2k^2}=0.320\mathrm{\&Omega;}$

R _Δ: open delta connects damping resistance; X _l: voltage transformer saturation reactance; X _cthe reactance of direct-to-ground capacitance; K: voltage transformer no-load voltage ratio; : n: the voltage transformer group number put into operation.Make R _Δvalue reaches minimum value, thus reaches best harmonic elimination effect.

(4) meet damping resistance R according to open delta _Δ≤ 0.32 Ω adjusts and completes microcomputer harmonic elimination device after harmonic elimination resistance value and install.

Above-described is only the preferred embodiment of the present invention, it should be pointed out that for the person of ordinary skill of the art, and under the prerequisite not departing from inventive concept, can also make some distortion and improvement, these all belong to protection scope of the present invention.

Claims (1)

1. a harmonic elimination method for power distribution station, is characterized in that: both a harmonic elimination apparatus and secondary resonance elimination device are used in conjunction with each other, step is as follows:

(1) certainty annuity parameter ω C, ω L, determines microcomputer harmonic elimination device model;

(2) select damping resistance value according to neutral point crosstalk resistance R0 >=0.056 ω L, meet damping resistance R Δ≤0.32 Ω according to open delta and to adjust harmonic elimination resistance value;

(3) complete neutral resistor to install, complete microcomputer harmonic elimination device and install.