JPH02123945A - Disconnection detector for field winding of synchronous machine - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an abnormality detection device for a synchronous machine that detects a break in a field winding of a synchronous machine.

(Prior Art) Conventionally, a break in the field winding on the rotor side of a synchronous machine has not been directly detected. In a synchronous machine that is running in parallel to the grid, an impedance relay installed on the armature side detects the phenomenon of field loss that occurs due to a break in the field winding or a failure in the excitation device, and the synchronous machine is operated in parallel. Protection measures such as suspension were in place. In addition, in the case of a synchronous generator that operates independently, protection was provided by stopping the generator due to an abnormal decrease in field current.

In these conventional protection methods, a protection operation is not performed until a nearly complete electrical disconnection state is reached. However, even if a mechanical break occurs in the field winding while the field current is flowing, the large inductance of the field winding acts to keep the current flowing until then. Therefore, even mechanically disconnected locations are connected by arcs, and electrically it does not easily become completely disconnected. If such a state (hereinafter referred to as a half-broken wire state) continues for a long time, the area around the arc occurrence location will be burned out by the arc. Depending on the structure of the rotor, partial repairs may not be possible and the entire rotor may have to be manufactured anew. In particular, cylindrical field rotors, in which field windings are loaded onto an iron core cut from a single steel ingot, often suffer partial damage that cannot be repaired.

(Problem to be solved by the invention) By the way, field windings are generally made of processed steel, and the temperature coefficient of their electrical resistance is large and stable. A rotor thermometer that detects the temperature of the field winding on the child side based on the field voltage and field current has been conventionally used. This means that the field voltage is Vf,
If the field current.

When the field winding resistance is Rf, in steady state, R
Since the field winding resistance is given by f=Vf/If, its R
The temperature of the field winding is calculated from the temperature coefficient of the winding material using f. In the half-open condition described above, the voltage required to pass the same current is higher by the arc voltage, so the rotor thermometer will indicate that the field winding temperature has increased. Therefore, it is conceivable to detect a half-disconnection state based on this temperature. However, the temperature is not much different from the normal temperature rise that can occur during high-load operation, and it is not possible to accurately detect the occurrence of a half-wire disconnection based only on the temperature.

It is also possible to detect a half-disconnection state by pulling out the middle point of the field winding outside and monitoring the voltage distribution on both sides of the middle point, but this is because the field winding in the rotor is It is not easy to implement the mechanical structure that requires the intermediate point to be brought out to the outside with the following changes.

It is an object of the present invention to solve the problem of disconnection of the synchronous machine field winding, including the half-disconnection state, which was difficult with the prior art as described above, without changing the mechanical structure of the synchronous machine field winding. The aim is to provide a device that can detect this.

In the following description, unless there is a particular need to distinguish, the term "broken wire state" includes both a semi-broken wire state and a completely broken wire state.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the synchronous machine field winding disconnection detection device of the present invention provides a field voltage that converts the field voltage applied to the field winding into an appropriate signal. A detector, a field voltage change amount detection means for inputting the field voltage signal obtained by the detector and determining the amount of change over time in the field voltage, and a field voltage change amount detection means for determining the amount of change in the field voltage over time; a field current detector that converts the field current signal into a signal, a field current change amount detection means for inputting the field current signal obtained by this detector and calculating the amount of change over time in the field current, and detecting the amount of change. and change state determining means for determining that a field voltage change amount signal and a field current change amount signal obtained from the means have a predetermined relationship,
It is characterized in that the operation of the change state determining means is a signal indicating the occurrence of a break in the field winding.

Further, a logical product means for calculating a logical product of any one or more of the four conditions (a) to (d) shown below and the operating condition of the change state determining means is provided, and the operation of the logical product means is A break in the field winding may also be detected.

(b) An active current detector that detects the active current of the synchronous machine and converts it into an appropriate signal, a change detection means that determines the amount of change in the effective current over time, and the amount of change is preset in either direction. a change state determination means for determining that the change state is in a state smaller than a value determined by the change state determination means, and a condition under which the change state determination means operates.

(b) A reactive current detector that detects the reactive current of the synchronous machine and converts it into an appropriate signal, a change detection means that determines the amount of change in the reactive current over time, and a change amount detection means that detects the amount of change in the reactive current over time. a change state determination means for determining that the change state determination means is in a state larger than a preset value in a smaller direction; and a condition under which the change state determination means operates.

('z)) A field ground fault detector is provided to detect ground faults in the field winding, and the conditions under which this field ground fault detector operates.

(d) Provided with an output signal detector that detects the output signal of the automatic voltage regulator of the synchronous machine and converts it into an appropriate signal, and excitation state determination means that determines that the output signal is the excitation strengthening signal of the synchronous machine. , the conditions under which this excitation state determining means operates.

(Function) When a half-wire break occurs, the field voltage increases by the arc voltage, and the field current decreases transiently as the arc occurs.

On the other hand, when the field winding is normal, the amount of change in field voltage and the amount of change in field current are in the same direction with respect to the current field voltage and current, respectively.

Therefore, the fact that the field voltage change amount ΔVfs continues to be in the increasing direction of the current field voltage and the field current change amount △Ifs is in the decreasing direction means that the circuit from the field voltage detection point to the field winding side continues. This indicates that a disconnection condition has occurred.

Therefore, the disconnection state of the field winding can be detected by this detection means.

In addition, any one of the four conditions (a) to (d) above is met.
Detection accuracy can be improved by making a judgment based on the logical product of two or more conditions and the operation of the change state judgment means that judges the disconnection state of the field winding from the field voltage change amount signal and the field current change amount signal. improves.

(Example 1) A first example of the present invention is shown in FIG. 1, and its configuration will be explained. 1 is the armature of the synchronous machine, and 2 is its field winding, which is usually located on the rotor side. 3 is an excitation device that supplies field current to the field winding, and an instrument voltage transformer 3A and an instrument current transformer 3B convert the voltage Vg of the armature 1 into a voltage signal vg.
This is a device for inputting a current signal Ias obtained by converting S and the current Ia of the armature 1 to the excitation device 3.

5 is a field voltage detector connected to both ends of the field winding, which converts the actual field voltage Vf into a signal Vfs suitable for subsequent equipment; 6 is a field current circuit shunt 4; A field current detector connected to the field current detector converts the actual field current If to a suitable signal Ifsk for subsequent equipment.

Reference numeral 7 denotes a field voltage change detection means that uses the field voltage signal Vfs as an input signal to obtain a field voltage change signal ΔVfs over time, and 8 uses the field current signal Ifs as an input signal to detect the field voltage change over time. Magnetic current change amount detection means This is a field current change amount detection means for determining ΔIfs.

9 is the field voltage change amount ΔVfs and the field current change amount ΔIfs
is the input signal, and each field voltage and field current are (ΔVfs>O) and (ΔVfs<
O).

Reference numeral 10 denotes a timer means which operates when the change state determining means 9 operates and continues for a preset fixed period of time to generate a signal OUT TSL indicating the occurrence of a disconnection of the field winding.

For the field voltage detector 5 and the field current detector 6, there are various commercially available isolation converters that insulate the voltage and current of the 1st power circuit and convert them into appropriate signals. The explanation of the configuration of is omitted.

Regarding other components 7 to 10 of this example,
The functions required of them are as explained above, and there are many types of specific electrical circuits that are publicly known to realize them, and these specific electrical circuits are not the point of the present invention, so we will explain them here. is omitted. Furthermore, since the functions required for the components 7 to 10 of this embodiment have been explained, it is extremely easy to realize these functions using a digital computer.

Field voltage change amount detection means 7 and field current change amount detection means 8
The change state determining means 9 can determine the change state of the field voltage and field current from the field voltage change amount signal ΔVfs and the field current change amount signal ΔIfs obtained in .

If there is no disconnection, the field voltage change signal ΔVfs and the field current change signal ΔIfs obtained from the change detection means 7 and 8 will show the same direction of change (increase or decrease). When a half-wire disconnection occurs, the field voltage increases by an amount equal to the arc voltage, while the field current transiently decreases as the arc occurs.

Generally speaking, when a half-wire disconnection occurs, the field voltage hardly changes, and the effect of actually flowing the field current decreases by the amount of the arc voltage, and as a result, it is thought that the field current decreases. However, the excitation device 3 has a voltage Vg of the armature 1 of the synchronous machine.
It is common to have an automatic voltage regulator AVR that adjusts the voltage to a constant value, and the AVR operation increases the field voltage so that the field current hardly changes.

As already explained, the change state determining means 9 operates when the field voltage change amount signal ΔVfs is in the increasing direction and the field current change amount signal ΔIfs is in the decreasing direction.

This is a state in which a disconnection occurs in the circuit from the field voltage detection point to the field winding side.

Therefore, the operation of the timer means 10 indicates that a disconnection condition has occurred in the field winding and has continued.

Therefore, according to this embodiment, a disconnection in the field winding of the synchronous machine is detected from the correlation between the amount of change in field voltage and the amount of change in field current. It is also possible to detect half-broken wires with low arc voltages that cannot be detected by this method alone.

(Example 2) In addition to the above-mentioned first example, it is determined that the field winding is in a disconnection condition by adding the AND condition that a phenomenon that is likely to cause the field winding to malfunction does not occur and other phenomena that occur when the field winding is disconnected. You can also do that. Due to the added AND condition, even if the portion of the first embodiment malfunctions, the final determination will not result in a disconnection state, so a more reliable detection device can be realized overall.

This second embodiment is shown in FIG. 2, and its structure and operation will be explained.

20 is an AND means, which outputs the output signal ○UTSI of the above embodiment.
and the conditions (a) to (d) described below, and the output signal OUTS2 is a signal indicating the occurrence of a disconnection in this embodiment.

(a) Reference numeral 11 denotes an active current detector which inputs the outputs of the instrument voltage transformer 3A and the instrument current transformer 3B, detects an effective current, and converts it into an appropriate signal. Its output is signal Ips
shall be.

Reference numeral 13 denotes a change amount detection means that receives the effective current signal Ips as an input and calculates the amount of change in the effective current over time;
Reference numeral 6 denotes change state determining means for determining the state of the output of the change amount detecting means 13. The change state determining means 16 detects that the temporal change in the effective current is smaller than a preset value in either direction. The specific configuration of these means will be explained later. This is added to the conditions for wire breakage detection in order to prevent the wire breakage detection device from malfunctioning when the field current suddenly changes due to an armature reaction caused mainly by an accident in the power system. Note that in this application, active power can be used as a completely equivalent signal instead of active current.

(b) A reactive current detector 12 receives the outputs of the instrument voltage transformer 3A and the instrument current transformer 3B, detects a reactive current, and converts it into an appropriate signal. Its output is the signal Iqs
shall be.

Reference numeral 14 denotes a change amount detection means that receives the reactive current signal Iqs as an input and determines the amount of change in the reactive current over time;
Reference numeral 7 denotes a change state determining means for determining the state of the output of the change amount detecting means 14. The change state determining means 17 detects that the temporal change in the reactive current is in the decreasing direction and is larger than a preset value. With this, it is possible to detect that the reactive current is decreasing over time. This is to add the phenomenon that occurs in the reactive current when the field winding is disconnected to the conditions for disconnection detection. Note that in this application, reactive power can be used as a completely equivalent signal instead of reactive current.

(c) A field ground fault detector 19 detects a ground fault in the field winding, and its operation signal Fgs is an input to the AND means 20. When the field winding is in a half-broken state, the field iron core, which is structurally grounded, and the field winding circuit have a very high probability of coming into contact with each other due to the generated arc, resulting in a field ground fault. On the other hand, if the condition is such that a field ground fault does not occur, even if a decision line condition occurs, there is little chance of major damage to the rotor.

This adds the phenomenon that occurs inside the rotor when the field winding is disconnected to the conditions for detecting disconnection.

(D) 15 is an AVR output signal detector that detects the output IAVR of the automatic voltage regulator (AVR) of the synchronous machine and converts it into an appropriate signal IAVR3. Reference numeral 18 denotes excitation state determining means which inputs the AVR output signal IAVR and compares it with a preset signal level to determine whether it is an excitation strengthening signal.The operation signal IEXs thereof is input to the AND means 20.

This is to add to the disconnection detection conditions the phenomenon that occurs in the output of the automatic voltage regulator when the field winding is disconnected.

Note that the gist of the present invention is not limited to adopting all of these (a) to (d) as an AND condition with the signal ○UTSI, but also includes adopting any one or more as an AND condition. It will be done.

Furthermore, as another embodiment, a timer means may be provided after the logical product means 20, and the disconnection state of the field winding can be determined when the logical product continues to be established for an appropriate period of time. In that case, the setting of the timer means 10 needs to be set to zero or smaller than when no timer means is provided after the AND means 20. Even if the timer means 10 is removed instead of setting the timer means 10 to zero, the gist of the present invention does not change.

In addition, it is possible to detect a condition opposite to the explained condition and use its negation as an input to the logical product means, or to use multiple logical product means to make the final logical judgment even if the above configuration is changed. can be made the same, and even if the above-described configuration is changed in this way, the gist of the present invention does not change.

〔Effect of the invention〕

According to the present invention, it is possible to detect not only a complete disconnection but also a half-disconnection state of the synchronous machine field winding, which was difficult in the past, without changing the mechanical structure of the synchronous machine field winding. . Therefore, it is possible to protect the synchronous machine rotor in a judgment state that has not been carried out in the past, so it is possible to prevent major damage to the synchronous machine rotor.
Moreover, since it is not necessary to change the mechanical structure of the synchronous machine field winding, it can be easily applied to existing synchronous machines, and the effects of the present invention are remarkable.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention, and FIG. 2 is a block diagram of a second embodiment of the present invention. 1... Armature 2... Field winding 3... Excitation device 3A... Instrument voltage transformer 3B... Instrument current transformer 4... Shunt switch 5... Field voltage Detector 6・
... Field current detector 7 ... Field voltage change amount detection means 8 ... Field current change amount detection means 9 ... Change state determination means lO ... Timer means 11 ... Effective current detection device 12...reactive current detector 13...active current change amount detection means 14...reactive current change amount detection means 15...AVR output signal detector 16...active current change amount determination means 17. ...Reactive current change amount determining means 18...Excitation state determining means 19...Field ground fault detector 20...Logic product means

Claims (2)

[Claims] (1) A field voltage detector that converts the field voltage applied to the field winding into an appropriate signal, and uses the field voltage signal obtained by this detector as input to measure the amount of change in the field voltage over time. A means for detecting the amount of change in field voltage to be sought; a field current detector that converts the field current supplied to the field winding into an appropriate signal; and a field current detector that converts the field current supplied to the field winding into an appropriate signal. Field current change amount detection means for determining the amount of change in the current over time;
Synchronization characterized by comprising change state determining means for determining that the field voltage change amount signal and the field current change amount signal obtained from the change amount detecting means have a predetermined relationship. Machine field winding disconnection detection device. (2) In the synchronous machine field winding disconnection detection device as set forth in claim 1, the following four items (a) to (d) are provided.
a logical product means for calculating the logical product of one or more of the above conditions and the operating condition of the change state determining means, and detecting a disconnection of the field winding by the operation of the logical product means. A disconnection detection device for a synchronous machine field winding, characterized by: (b) An active current detector that detects the active current of the synchronous machine and converts it into an appropriate signal, a change detection means that determines the amount of change in the effective current over time, and the amount of change is preset in either direction. a change state determination means for determining that the change state is in a state smaller than a value determined by the change state determination means, and a condition under which the change state determination means operates. (b) A reactive current detector that detects the reactive current of the synchronous machine and converts it into an appropriate signal, and a change detection means that determines the amount of change in the reactive current over time, and if the amount of change is higher than the current reactive current. a change state determination means for determining that the change state determination means is in a state larger than a preset value in a smaller direction; and a condition under which the change state determination means operates. (c) A field ground fault detector is provided to detect ground faults in the field winding, and the conditions under which this field ground fault detector operates. (d) An output signal detector that detects the output signal of the automatic voltage regulator of the synchronous machine and converts it into an appropriate signal, and an excitation state determination means that determines that the output signal is an excitation strengthening signal of the synchronous machine, Conditions under which this excitation state determination means operates.