CN206038891U - Current transformer secondary identification system that opens a way - Google Patents

Abstract

The utility model provides a current transformer secondary identification system that opens a way, including the CT secondary detection device that opens a way, CT secondary winding, protection device A and protection device B, the CT secondary is opened a way detection device and is set up between CT secondary winding and two protection device, CT secondary winding includes by A looks first winding, the first secondary current of group that B looks first winding and C looks first winding constitute, and by A looks secondary winding, the secondary current of second group that B looks secondary winding and C looks secondary winding are constituteed, and two sets of secondary current open a way detection device through the CT secondary and flow in protection device A and protection device B respectively. Open a way identification method and all have certain limitation in order to solve current current transformer secondary, can't satisfy the current transformer secondary problem that real -time detection's reality required of opening a way for under any circumstance, can both effectual detect out the current transformer secondary trouble of opening a way. The utility model belongs to the relay protection field.

Description

A kind of Current Transformer Secondary open circuit identifying system

Technical field

This utility model is related to Current Transformer Secondary open circuit identifying system, belongs to relay protection field.

Background technology

Current transformer (abbreviation CT) is widely used in power system, and its first winding is serially connected with high voltage circuit, and two Secondary winding is connected with measuring instrumentss, protection device, is related to the accuracy of measuring, the reliability of protective relaying device and height The safety of volt circuit.During normal work, CT secondary sides are near short circuit state, and output voltage is very low, if in operation two Secondary winding open circuit can produce thousands of volts even overvoltage of volts up to ten thousand in secondary side, and this can not only make CT too drastic and scaling loss, or even Jeopardize the life security of staff, and cause heavy economic lossess, therefore prevent Current Transformer Secondary from opening a way, research is effective Current Transformer Secondary open circuit recognition methodss it is significant.

Existing Current Transformer Secondary open circuit recognition methodss mainly have secondary current voltage block method and overvoltage protection method Two big class.

1st, secondary current voltage identification method, predominantly relay protection producer are adopted, by the electric current to accessing protection device Transformer secondary side three-phase current and three-phase voltage carry out logic discrimination, and the concrete criterion of each producer is not quite similar, substantially adopts With there is discriminant approach of the zero-sequence current without residual voltage.When the disconnected phase of certain phase current mutual inductor secondary side, the phase current disappears, its He is biphase normal, it will produce zero-sequence current, now once no ground failure, residual voltage very little, by have zero-sequence current without The method of residual voltage differentiates Current Transformer Secondary broken string.The method is less in load current or three-phase cannot be judged when breaking CT second open circuit failures, it is impossible to which guarantee can determine the requirement of CT second open circuits in any case.

2nd, secondary overvoltage detection method, when mainly using normal work, Current Transformer Secondary side is near short circuit shape State, output voltage are very low, if can produce abnormal peak overvoltage in secondary side after current transformer second open circuit in operation Principle, by detect CT secondary side voltages judge whether occur CT second open circuits, if Current Transformer Secondary side voltage reaches Setting value then overvoltage relay action, it is believed that CT secondary sides occur open circuit.The method of discrimination can produce erroneous judgement to Lightning Over-voltage, Judge Current Transformer Secondary open circuit when causing normally to run by accident.

As can be seen here, existing Current Transformer Secondary open circuit recognition methodss have certain limitation, it is impossible to meet electric current The actual requirement of transformer second open circuit real-time detection.

The content of the invention

The purpose of this utility model is：A kind of Current Transformer Secondary open circuit identifying system is provided, to solve existing electricity Current transformer second open circuit recognition methodss have certain limitation, it is impossible to meet showing for Current Transformer Secondary open circuit real-time detection The real problem for requiring so that under any circumstance, can effectively detect Current Transformer Secondary open fault.

For solving the above problems, there is provided a kind of Current Transformer Secondary open circuit identifying system, detect including CT second open circuits Device, CT Secondary Windings, protection device A and protection device B, CT second open circuit detection means are arranged at CT Secondary Windings and two Between protection device, CT Secondary Windings include the first winding of A phases, the first winding of B phases, the first winding of C phases, the second winding of A phases, B The second winding of the second winding of phase and C phases, the first winding of A phases, the first winding of B phases and the first winding of C phases constitute first group of secondary electricity Stream, the second winding of A phases, the second winding of B phases and the second winding of C phases constitute second group of secondary current, and two groups of secondary currents pass through CT second open circuit detection means separately flows into protection device A and protection device B, while CT secondary winding electric currents are monitored, CT Second open circuit detection means also monitors the overvoltage of each Secondary Winding, the such as 1SA and 1SAN of monitoring A the first windings of phase both sides it Between overvoltage.

In aforementioned currents transformer second open circuit identifying system, CT second open circuits detection means and protection device A and B are Existing apparatus, such as CT second open circuits detection means are An Kerui ACTB-3 transformer open-circuit-protection voltage protectors or dragon nation LB/ CTKB-9D type CT second open circuit protectors.

Compared with prior art, system described in the utility model by current transformer difference windings electric current difference with it is secondary Side open-circuit voltage criterion combines, and solves that conventional second open circuit method of discrimination is little to current capacity, three-phase is while broken string cannot Effectively the problem of judgement and lightning surge erroneous judgement, provides new reliable judgement system for Current Transformer Secondary open circuit.

Description of the drawings

Fig. 1 is this utility model Current Transformer Secondary open circuit detecting system general structure schematic diagram；

Fig. 2 is the flow chart of this utility model Current Transformer Secondary open circuit recognition methodss.

Specific embodiment

For making the purpose of this utility model, technical scheme and advantage clearer, this utility model will be made into one below Step ground is described in detail,

Embodiment：

Current Transformer Secondary open circuit identifying system as shown in Figure 1, including CT second open circuits detection means 1, CT bis- times Winding, protection device A2 and protection device B3, CT second open circuits detection means 1 are arranged at CT Secondary Windings and two protection devices Between, CT Secondary Windings include the first winding of A phases 7, the first winding of B phases 8, the first winding of C phases 9, the second winding of A phases 4, B phases Two windings 5 and the second winding of C phases 6, the first winding of A phases 7, the first winding of B phases 8 and the first winding of C phases 9 constitute first group of secondary electricity Stream, the second winding of A phases 4, the second winding of B phases 5 and the second winding of C phases 6 constitute second group of secondary current, and two groups of secondary currents lead to Cross CT second open circuits detection means 1 and separately flow into protection device A2 and protection device B3, in the same of monitoring CT secondary winding electric currents When, CT second open circuits detection means 1 also monitors the overvoltage of each Secondary Winding, such as the 1SA of 7 both sides of the first winding of monitoring A phases Overvoltage between 1SAN, to judge to the step 4 in scheme.

The flowchart representation of Fig. 2 this utility model Current Transformer Secondary open circuit recognition methodss, step are as follows：

(1) same current transformer has multigroup Secondary Winding, introduces two groups of different windings in Current Transformer Secondary side Secondary current, A, B, C three-phase current simultaneously introduces, and can now obtain current sample group I of two A, B, C three-phases_1φAnd I_2φ, together When measure two windings every phase secondary voltage, the voltage of two A, B, C three-phases can be obtained using organizing a U_1φAnd U_2φ, wherein I₁Table Show first group of current sample, I₂Represent second group of current sample, U_1φRepresent first group of open-circuit voltage sampling, U_2φRepresent second group Open-circuit voltage is sampled, replacing representations of the φ for A, B, C three-phase.

(2) judge set of samples I_1φAnd I_2φWhether CT saturations, the return to step 1 if CT saturations are entered if CT unsaturations Enter next step.During CT saturations, sampled value is the non-linear change of disease, the electric current difference that different secondary winding is exported, no comparability.CT Saturation can differentiate CT whether saturations with the secondary and triple-frequency harmonics content in secondary current.

(3) according to formula：|I_1φ-I_2φ| ＞ K (| I_1φ|+|I_2φ|) judged, enter next if formula is set up Step, return to step 1 if being false.In formula, K is coefficient of reliability, is taken between 0.6-0.8, and when being embodied as, K takes 0.6.

(4) according to formula：U_1φ＞ U_setOr U_2φ＞ U_setJudged, if U_1φ＞ U_setSet up, then time delay is for a period of time Judge after T1 that first via φ phase secondary current is opened a way, while CT open circuit block signals are sent to protection device A, time delay is for a period of time By CT second open circuit device actions first group of CT winding of short circuit after T2.If U_2φ＞ U_setSet up, then time delay is for a period of time after T1 Judge the second road φ phases secondary current open circuit, while CT open circuit block signals are sent to protection device B, time delay is for a period of time after T2 By CT second open circuit device actions second group of CT winding of short circuit.The return to step 1 if above-mentioned two formula is false.U in formula_set For second open circuit voltage setting value, take between 0-600 volts, delay time T1 was taken between the 0-30 seconds, and T2 was taken between the 0-5 seconds.Specifically U during enforcement_set300 volts are taken, T1 takes 0.2S, T2 takes 0.1 second.

One given below uses example, is broken with first group of A phase CT, and other are normal, and saturation does not occur, and failure continue for As a example by 0.4 second.First group, second group of electric current, voltage are sampled, I is obtained_1A、I_2A、U_1A、U_2A。

Break in first group of A phase, in the case of other are normal, I_1A=0, detect U_1AAnd its value is more than U_set, I_2AJust Often, U_2A=0.Step 3 is entered according to Fig. 2 in the case where there is no CT saturations, it is clear that formula：|I_1A-I_2A| ＞ 0.6 (| I_1A|+| I_2A|) set up.Into step 4, when first group of current transformer A phase breaks, high voltage, i.e. U can be produced in its secondary side_1A＞ U_setMeet, time delay judges that first via A phase secondary current is opened a way for 0.2 second, while CT open circuit block signals are sent to protection device A, Latch-up protection device is in order to avoid cause malfunction, then time delay 0.1 second, by CT second open circuit device actions first group of CT winding of short circuit, CT is opened Road failure vanishes.

Finally it should be noted that foregoing description is only preferred embodiment of the present utility model, the common skill of this area Art personnel on the premise of without prejudice to this utility model objective and claim, can be made under enlightenment of the present utility model Represent as multiple types, such conversion is each fallen within protection domain of the present utility model.

Claims (1)

1. a kind of Current Transformer Secondary is opened a way identifying system, it is characterised in that：Including CT second open circuit detection means (1), CT Secondary Winding, protection device A (2) and protection device B (3), CT second open circuit detection means (1) are arranged at CT Secondary Windings and two Between individual protection device, CT Secondary Windings include the first winding of A phases (7), the first winding of B phases (8), the first winding of C phases (9), A phases Second winding (4), the second winding of B phases (5) and the second winding of C phases (6), the first winding of A phases (7), the first winding of B phases (8) and C phases First winding (9) constitutes first group of secondary current, the second winding of A phases (4), the second winding of B phases (5) and C phases the second winding (6) group Into second group of secondary current, and two groups of secondary currents separately flow into protection device A (2) by CT second open circuit detection means (1) With protection device B (3).