CN217931884U

CN217931884U - Generator export PT interturn insulation fault on-line diagnosis system

Info

Publication number: CN217931884U
Application number: CN202220367336.1U
Authority: CN
Inventors: 吴永兵; 陈泽荣; 郑灿
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-02-23
Filing date: 2022-02-23
Publication date: 2022-11-29
Anticipated expiration: 2032-02-23

Abstract

The utility model relates to a generator equipment detects technical field, and discloses a generator export PT interturn insulation fault on-line diagnosis system, include the PT that links to each other with the three-phase alternating current, be connected with CT1, CT2, CT3, CT4 and CT5 on the PT, CT1 links to each other with PT primary side power supply circuit, pass CT2, CT3 and CT4 on the PT secondary side coil, and all be connected with the load, CT5 links to each other with PT secondary circuit ground terminal, CT1, CT2, CT3, CT4 and CT5 all link to same oscillograph, the oscillograph passes through digital signal with the monitoring host computer and is connected; the monitoring device realizes real-time measurement of state characteristic quantity under PT operating voltage, and the specific parameters are as follows: when early warning information (turn-to-turn short circuit) appears, the system gives out preliminary diagnosis suggestions and suggestion points of attention by combining state judgment information, and guides maintainers to carry out fault detection and maintenance in a targeted manner.

Description

Generator export PT interturn insulation fault on-line diagnosis system

Technical Field

The utility model relates to a generator equipment detects technical field, specifically is a generator export PT interturn insulation fault online diagnosis system.

Background

The large-scale 300MW and above generator outlet side PT is used as main equipment of a power plant, has important functions of outlet voltage measurement, generated energy measurement, relay protection, voltage acquisition of an excitation system and the like, and in case of failure, the safe and stable operation of the generator set is seriously influenced, and even the generator set is caused to be shut down in an unplanned manner.

Common faults of a PT on the outlet side of the generator include a primary winding turn-to-turn short circuit, a primary fuse fusing, single-phase grounding and the like. In recent years, power generation enterprises at home and abroad have a plurality of non-stop events caused by turn-to-turn short circuit of an export PT winding. Taking a certain power generation company as an example, from the fourth quarter of 2016 to the end of 2017, 5 unit non-stop events caused by outlet PT faults occur, wherein 4 times are primary winding turn-to-turn short circuit faults. The turn-to-turn short circuit problem of the export PT becomes a weak link which seriously influences the safe operation of a unit and a prominent problem to be solved urgently. The phase A of the output PT (model: JDZJ-20) of the second thermal power plant #3 generator of the head of the cigarette in 5, 7 and 2021 is burnt, and cracks appear on the outer surface, so that the generator trips. 2012. 35Kv bus PT (JDZX 9-35) A phase of a third wind farm of Huanen Bay of 2 Ri.7.3 is exploded, causing tripping of the unit.

Aiming at the problem of slight turn-to-turn short circuit of the PT winding, the protection locking logic of the existing running relay protection device is not perfect, equipment faults can not be effectively found at the initial stage of the faults, and the functions can be played only when the faults are developed to the serious turn-to-turn short circuit stage. The conventional power failure detection method for PT turn-to-turn short circuit includes direct current resistance test, transformation ratio test, no-load current test and the like, but power failure detection can only be used as a pre-test or a detection means after an accident occurs, and the fault is confirmed after the accident occurs and causes non-stop, so that serious equipment damage and economic loss are often caused at the moment. Therefore, compared with power failure detection, how to realize early diagnosis and rapid early warning of the PT turn-to-turn short circuit fault at the outlet of the generator in operation by a technical means is very important.

Compared with the traditional regular maintenance, the condition maintenance can determine the maintenance time and the maintenance strategy according to the equipment condition, and is a necessary trend of future power equipment maintenance development. The online monitoring is the basis and basis for realizing the state maintenance, is widely applied to the power system, and has important significance for improving the safe and stable operation of the power system. The method mainly searches for an early diagnosis method of PT turn-to-turn insulation defects through methods such as theoretical simulation, experimental research and the like, and provides a theoretical basis for realizing transformer insulation defect monitoring.

At present, the PT (potential transformer) turn-to-turn or interlayer insulation detection means at the outlet of the generator is mainly off-line detection, and all technical means are PT detection performed in the power failure state of the generator. (among them, direct current resistance measurement, no-load current measurement, lightning impulse withstand voltage, alternating current withstand voltage, partial discharge measurement, etc.).

At present, a direct current resistance test and a no-load current test are more suitable for diagnosing faults after the faults are detected, and the detection of early insulation defects is not sensitive enough; the lightning impulse withstand voltage belongs to destructive tests, can be developed only before delivery, and is influenced by the distributed capacitance among turns and layers of a primary winding and the capacitance to ground, and the method has no obvious effect on detecting the defects of an inner-layer coil close to an iron core; the alternating current withstand voltage is divided into a power frequency withstand voltage test and a frequency doubling withstand voltage induction test, and the test voltage of the power frequency withstand voltage test is 2-3 times of the rated voltage of the equipment. When such a high test voltage is applied to the PT, the iron core is saturated severely, so that it is practically impossible to perform a frequency-dependent voltage withstand test. However, the generator cannot be realized during operation, and the frequency is not consistent. The potential danger of turn-to-turn insulation is difficult to discover (the potential danger of PT is not detected by adopting the frequency doubling withstand voltage induction test and direct current resistance method for the generator of the #2 unit of the Huanen solar logical power plant in 11 months in 2021, and the excessive local discharge amount is found to exceed one time only in the local discharge test); partial discharge measurement is an effective means for PT defect detection, but has strict requirements on electromagnetic environment, and can be effectively carried out only in a laboratory or a unit power failure state, and the method has certain omission of coils at a low potential, such as: the fully insulated PT with the partial discharge defect exists, and the partial discharge quantity measured by grounding the A end and the N end respectively also has obvious difference.

SUMMERY OF THE UTILITY MODEL

Technical problem to be solved

The utility model provides a not enough to prior art, the utility model provides a generator export PT interturn insulation fault on-line diagnosis system possesses the detection to slight interturn short circuit, can monitor the change of a circle short circuit even, PT/CT is situated between and decreases measuring result accurate, adopt cross-core mutual inductor, can not cause the influence to equipment, do not influence the safe operation of equipment, to the especially sensitive advantage of early fault's comprehensive monitoring, whether the generator export PT of being not convenient for when having solved the generator operation has been foreseen and whether has the problem of slight interturn short circuit.

(II) technical scheme

In order to achieve the above object, the utility model provides a following technical scheme: the utility model provides a generator export PT interturn insulation fault on-line diagnosis system, includes the PT that links to each other with three-phase alternating current, be connected with CT1, CT2, CT3, CT4 and CT5 on the PT, CT1 links to each other with the power, CT2, CT3 and CT4 all are connected with the load, CT5 links to each other with PT secondary circuit earthing terminal, CT1, CT2, CT3, CT4 and CT5 all link to same oscillograph, the oscillograph passes through digital signal connection with the control host computer.

Preferably, the PT are provided with nine groups.

Preferably, the CT1, the CT2, the CT3, the CT4 and the CT5 are all through CTs.

(III) advantageous effects

Compared with the prior art, the utility model provides a generator export PT interturn insulation fault on-line diagnosis system possesses following beneficial effect:

the monitoring device realizes real-time measurement of state characteristic quantity under PT operating voltage, and the specific parameters are as follows: when early warning information (turn-to-turn short circuit) appears, the system gives out preliminary diagnosis suggestions and suggestion points of attention by combining state judgment information, and guides maintainers to carry out fault detection and maintenance in a targeted manner.

Drawings

FIG. 1 is a schematic diagram of an excitation current measurement method;

FIG. 2 is a schematic diagram of online measurement of leakage current;

FIG. 3 is a schematic diagram of dielectric loss on-line measurement;

FIG. 4 is a schematic diagram of an on-line measurement of high frequency partial discharge;

FIG. 5 is a schematic view of an on-line vibration-based measurement;

fig. 6 is a circuit diagram of a simulation test according to the present invention;

FIG. 7 is a graph showing the variation of the exciting current with the number of short circuit turns when 5KV is applied to the primary side;

FIG. 8 is a graph showing the change of the phase angle difference with the number of short circuit turns when 5KV is applied to the primary side;

FIG. 9 is a circuit diagram of the method of the present invention;

fig. 10 is an equipment assembly diagram of the system of the present invention;

fig. 11 is a schematic diagram of a system according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

Examples

This utility model proposes 300MW generator export PT and is the research object, through research PT under power frequency operating condition, whether voltage transformer PT is reacted to the voltage U2 of secondary side measurement coil two ends and the change amount of side coil exciting current I0 phase angle, has the short circuit phenomenon of early 1 ~ 2 circles. The generator tripping accident caused by PT inter-turn insulation fault similar to the generation of a second power plant with a Bay and a third wind field of a bridge is avoided.

Excitation current amplitude and phase: the following can be obtained according to the formula:

wherein: n1: the number of turns of the PT primary coil winding; i all right angle ₁ Is the current measured by the primary loop CT 1.

N2: the number of turns of a PT secondary winding; i all right angle ₂ Is the current measured by the secondary loop CT 2.

N3: the number of turns of a PT secondary winding; i all right angle ₃ Is the current measured by the secondary loop CT 3.

N4: the number of turns of a PT secondary certain winding; i.e. i ₄ Is the current measured by the secondary loop CT 4.

At present, the domestic 20KvPT insulation and turn-to-turn detection method comprises the following steps:

however, in recent years, with the development of computer technology, new technologies have emerged:

(1) The primary and secondary winding voltage and current variations are used to monitor whether a fault has occurred. Because the original and secondary side voltage and current change values are very small when the turn-to-turn short circuit fault occurs, and the load is dynamic in the actual operation of the PT, the current is continuously changed, and the change amplitude of the PT is far more than the change amplitude of the turn-to-turn short circuit fault, so that the influence of the change on the turn-to-turn short circuit fault is difficult to eliminate;

(2) Whether a fault occurs is monitored by using the change of a leakage magnetic field when the PT is in short circuit. When the PT has turn-to-turn short circuit fault, the change of a leakage magnetic field is obvious, the turn-to-turn short circuit fault can be monitored by detecting the change of leakage magnetic flux by using a detector, but the method needs to put a detection coil into the PT, and the turn-to-turn short circuit fault of a winding is monitored by measuring the change of induced voltage in the detection coil, which influences the performance of equipment;

(3) Turn-to-turn shorts are monitored by measuring power loss. When winding equipment generates turn-to-turn short circuit, the internal power loss of the winding equipment is obviously increased, and the power of PT is calculated by utilizing the voltage and the current magnitude of each side of the PT, so that the change of the loss is obtained. Errors introduced by the current transformers and PT used to measure current and voltage also affect the evaluation of the measurements.

Referring to fig. 1-5, the current domestic development of online detection means for Potential Transformer (PT) turn-to-turn hazards has the following advantages and disadvantages:

1) The excitation current measuring method has the advantages that the method for monitoring the current of the PT high-voltage side is simple, but the current of the high-voltage side changes with the voltage and the load;

2) The leakage current is measured on line, and the method for monitoring the PT/CT leakage current has the advantages that the method is easy to realize, but is greatly influenced by temperature, humidity and dirt;

3) Dielectric loss on-line measurement, which is realized by monitoring the dielectric loss of PT/CT, but is greatly influenced by temperature and humidity, and has large measurement error;

4) The high-frequency partial discharge online measurement has the advantages that the realization is simple, but the influence by environmental interference is large, and the investment is high by a method for monitoring the PT/CT partial discharge amount;

5) The method for monitoring the PT/CT vibration characteristics based on vibration online measurement has the advantages of simple realization, large influence by environmental interference and difficult identification.

Referring to fig. 6-8, first, a PT inter-turn short circuit model on the outlet side of the generator is constructed, and then a simulation test is performed by studying an excitation current variation law under a small quantity of PT inter-turn unstable breakdown defects to obtain simulation test data (see the following table)

Referring to fig. 7, it can be seen that the exciting current detected by the high-voltage side winding is in an increasing trend with the increase of the number of short-circuit turns, but the method for reflecting the PT turn-to-turn short circuit still has a limitation, and the exciting current is increased synchronously with the increase of the voltage, and cannot be accurately determined.

Referring to fig. 8, it can be seen that as the number of short-circuit turns increases, the phase angle difference between the phase angle of the secondary voltage U2 and the phase angle difference between the phase angles of the exciting currents i 0 of the primary coils is obviously decreased in a cliff-like manner, and whether the turn-to-turn short circuit exists in PT can be determined by using the characteristic.

Referring to fig. 9 to 11, the online diagnosis system for the PT turn-to-turn insulation fault at the outlet of the generator comprises a PT connected with a three-phase alternating current, wherein the PT is connected with a CT1, a CT2, a CT3, a CT4 and a CT5, the CT1 is connected with the N pole of a primary side power supply of the PT, the CT2, the CT3 and the CT4 are connected with a load, the CT5 is grounded, the CT1, the CT2, the CT3, the CT4 and the CT5 are connected to the same oscillograph, and the oscillograph is connected with a monitoring host through digital signals.

In this embodiment, the PTs include nine groups.

In this embodiment, CT1, CT2, CT3, CT4, and CT5 are all straight-through CTs.

In this embodiment, the voltage signals collected by the current signals i 1, i 2, i 3, i 4 of the 9 PT groups through CTI, CT2, CT3, CT4 and the small PT (100/3.53) on the secondary CT2 loop are sent to the recorder to be transmitted to the recorder to draw digital signals. And transmitting the data to a monitoring host for data analysis and comparison. And monitoring whether the potential danger of turn-to-turn short circuit exists at an outlet PT of the generator.

In this embodiment, CT1, CT2, CT3, CT4, and CT5 of the device; CT with the following parameters can be used:

the model is as follows: XJS-500;

specification: 500mA/500uA;

a small PT on the secondary side of the device; PT with the following parameters can be used:

the model is as follows: LXYA;

specification: 100V/3.53V;

remote transmission communication:

100Mbps single-mode fiber TCP/IP Modbus for Ethernet;

RS485 twisted pair cable Modbus;

the monitoring host can adopt a computer.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. The utility model provides a generator export PT interturn insulation fault on-line diagnosis system which characterized in that: include the PT that links to each other with the three-phase alternating current, be connected with CT1, CT2, CT3, CT4 and CT5 on the PT, CT1 links to each other with the power, CT2, CT3 and CT4 all are connected with the load, CT5 and PT secondary circuit earthing terminal link to each other, CT1, CT2, CT3, CT4 and CT5 all are connected to same oscillograph, the oscillograph passes through digital signal with the control host computer and is connected.

2. The system for online diagnosis of the turn-to-turn insulation fault of the PT outlet of the generator according to claim 1, wherein: the PT are provided with nine groups.

3. The system for online diagnosis of PT turn-to-turn insulation fault at the outlet of a generator according to claim 1, characterized in that: the CT1, the CT2, the CT3, the CT4, and the CT5 are all straight-through CTs.