CN105403779B - A kind of DC line fault recognition methods based on polar curve current gradient sum - Google Patents
A kind of DC line fault recognition methods based on polar curve current gradient sum Download PDFInfo
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- CN105403779B CN105403779B CN201510633235.9A CN201510633235A CN105403779B CN 105403779 B CN105403779 B CN 105403779B CN 201510633235 A CN201510633235 A CN 201510633235A CN 105403779 B CN105403779 B CN 105403779B
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
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Abstract
The present invention relates to a kind of DC line fault recognition methods based on polar curve current gradient sum, belong to Relay Protection Technology in Power System field.After metallic earthing failure occurs for HVDC transmission line, the latter current value of the neighbouring sample point measured using measuring end subtracts previous current value, and the two difference and the ratio in sampling interval are defined as current gradient.Fixed length is time window length before choosing current sampling point, is summed to the current gradient in wherein all sampling intervals, obtained value be defined as current sampling point current gradient and.When the current gradient of continuous five sampled points of measuring end and both greater than setting valve, then line-internal failure has occurred in judgement；When the current gradient of continuous five sampled points of measuring end and both less than setting valve, then route external fault has occurred in judgement.A large amount of emulation show to differentiate that this method is reliable and precision is high for fault type.
Description
Technical field
The present invention relates to field of relay protection in power, specifically a kind of direct current based on polar curve current gradient sum
Line fault recognition methods.
Background technique
Direct current transportation is more and more widely used in power Transmission due to its peculiar advantage.DC power transmission line
Distance, across area surroundings complexity, the probability to break down is big.For DC line fault, failure process and its dynamic
Characteristic and DC control effect are closely related, so that DC control system is to DC line protection, especially to back-up protection
Influence can not be ignored.The route protection of present engineering practice is mainly to make by the traveling-wave protection of core of electrical change rate
For main protection.The protection in distal end high resistant tends to that tripping occurs.Therefore, it is necessary to study new direct current protecting calculation
Method can not only identify route high resistive fault, and actuation time is much smaller than existing differential protection.Using smoothing reactor and
The physical boundary that DC filter is constituted is to the attenuation of high fdrequency component, so that line-internal failure and external fault measuring end
Electric current high frequency content have differences.Algorithm provided by the invention is namely based on this principle, existing 10KHz is sampled blunt
Flow Line protection, fault zone can be identified by not needing lightning stroke disturbance ecology element.
Summary of the invention
The technical scheme is that after metallic earthing failure occurs on HVDC transmission line, due to flat wave electricity
The electrical boundary that anti-device and filter are constituted has very strong attenuation to high-frequency signal, to line-internal failure and route outside
High fdrequency component contained by the electric current that portion's failure measuring end measures is different.The fault current difference of neighbouring sample point is measured to measuring end
Current gradient is constructed, the current gradient summation in window all sampling intervals when to before current sampling point.If measuring end continuous five
Sampled point current gradient and both greater than setting valve, then line-internal failure has occurred in judgement；Otherwise, judgement has occurred outside route
Portion's failure.Accordingly, line fault recognition methods is obtained.
It is characterized in that line-internal failure and route external fault current gradient and different specific step is as follows:
(1) it is using the gradient of polar curve electric current calculating current neighbouring sample point amplitude variation
Di (k)=(i (k)-i (k-1))/Δ t (1)
In formula: the current sampled point that k is indicated, △ t indicates the sampling interval, as unit of ms.
(2) with S (k) indicate current gradient and, i.e.,
And obtain the stepping type of (2)
S (k)=S (k-1)+(i (k)-i (k-1))/Δ t
Wherein, i (k), i (k-1) indicate the current value on sampled point k, k-1, sampling number when N is in window, SsetIt protects
Protect definite value；
(3) under the sample rate of 10kHz.According to formula (2), the fault element criterion for obtaining S (k) construction is
|S(k)|≥Sset (3)
When continuous three points of starting element are both greater than setting valve, then starting is protected, after starting, first value is denoted as S
(k).If having in 4 sampling intervals of broadening | S (k) |, | S (k+1) |, | S (k+2) |, | S (k+3) | and | S (k+4) | it is all larger than
Sset, SsetIt is taken as 1.5pu, then is judged as line fault, it is on the contrary then be judged as route external fault.
The beneficial effects of the present invention are:
(1) this method is to realize seeking for polar curve current gradient sum based on real time data, thus to identify line-internal event
Barrier and external fault, criterion are succinct.
(2) can alleviate using du/dt as the traveling-wave protection of core since transition electricity has occurred in the discreteness or route of sampling
Hinder the case where slightly higher high resistive fault does not reach protection definite value and makes relay fail.
Detailed description of the invention
Fig. 1 is its measuring end fault current of electrode line road failure and its S (k).
Fig. 2 is the fault current and its S (k) of rectification side AC system singlephase earth fault anode route measuring end.
Fig. 3 is the wide ± 800KV DC transmission system structure chart of cloud.Rectification side exchanges side reactive compensation capacity with inverter side
Respectively 3000 and 3040Mvar, every pole convertor unit are composed in series by 2 12 pulse inverters, and DC power transmission line overall length is
1500km.Route two sides fill the smoothing reactor of 400mH, and DC filter is 12/24/36 three-tuned filter, and rectification flanks
Earth polar total track length is 109km, and inverter side ground electrode circuit overall length is 112km.
Specific embodiment
Embodiment 1: ± 800KV DC power transmission line as shown in figure 3, DC line boundary by route depending on the equivalent circuit that enters
As shown in Figure 4.Metallic earthing failure, sample frequency 10kHz occur for electrode line distance M end 10km.
(1) gradient and S (k) are sought to fault current according to step (1)~(2).
(2) obtain S (k), S (k+1), S (k+2), S (k+3), S (k+4) be followed successively by 10.35 respectively, 14.81,14.96,
16.96,18.56, it is all larger than 1.5pu, is judged as line-internal failure criterion.
Embodiment 2: ± 800KV DC power transmission line as shown in figure 3, DC line boundary by route depending on the equivalent circuit that enters
As shown in Figure 4.Electrode line distance M end 750km, occurs ground fault, and transition resistance is 100 Ω.
(1) gradient and S (k) are sought to fault current according to step (1)~(2).
(2) obtain S (k), S (k+1), S (k+2), S (k+3), S (k+4) be followed successively by 13.100 respectively, 3.630,4.29,
4.561,4.613, it is all larger than 1.5pu, is judged as line-internal failure criterion.
Embodiment 3: ± 800KV DC power transmission line as shown in figure 3, DC line boundary by route depending on the equivalent circuit that enters
As shown in Figure 4.Side outlet failure is rectified, transition resistance is 100 Ω.
(1) gradient and S (k) are sought to fault current according to step (1)~(2).
(2) obtain S (k), S (k+1), S (k+2), S (k+3), S (k+4) be followed successively by 0.035 respectively, 0.289,0.422,
0.641,0.633, it is less than 1.5pu, is judged as route external fault criterion.
Claims (1)
1. a kind of DC line fault recognition methods based on polar curve current gradient sum, it is characterised in that: high-voltage dc transmission electric wire
After metallic earthing failure occurs for road, since the electrical boundary that smoothing reactor and filter are constituted has very high-frequency signal
Strong attenuation, thus for line-internal failure and route external fault, high frequency division contained by the electric current that measuring end measures
Amount is different；The fault current difference for measuring neighbouring sample point to measuring end constructs current gradient, window when to before current sampling point
The current gradient in interior all sampling intervals is summed, if the continuous five sampled point current gradients of measuring end and both greater than setting valve, that
Line-internal failure has occurred in judgement；Otherwise, route external fault has occurred in judgement；
Specific step is as follows:
(1) gradient of polar curve electric current calculating current neighbouring sample point amplitude variation is utilized are as follows:
Di (k)=(i (k)-i (k-1))/Δ t (1)
In formula: the current sampled point that k is indicated, △ t indicates the sampling interval, as unit of ms；
(2) with S (k) indicate current gradient and, it may be assumed that
And obtain the stepping type of (2):
S (k)=S (k-1)+(i (k)-i (k-1))/Δ t
Wherein, i (k), i (k-1) indicate the current value on sampled point k, k-1, sampling number when N is in window, SsetProtection is fixed
Value；
(3) under the sample rate of 10kHz, according to formula (2), the fault element criterion of S (k) construction is obtained are as follows:
|S(k)|≥Sset (3)
When continuous three points of starting element are both greater than setting valve, then starting is protected, after starting, first value is denoted as S (k)；If
In 4 sampling intervals of broadening, have | S (k) |, | S (k+1) |, | S (k+2) |, | S (k+3) | and | S (k+4) | it is all larger than Sset,
SsetIt is taken as 1.5pu, then is judged as line fault, it is on the contrary then be judged as route external fault.
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| CN106841925B (en) * | 2017-03-09 | 2019-12-03 | 昆明理工大学 | A kind of direct current transmission line fault based on filter branches current gradient sum selects pole method |
| CN107390046B (en) * | 2017-06-19 | 2019-08-30 | 天津大学 | A kind of high voltage direct current transmission line fault type judgement method |
| CN109425838B (en) * | 2017-08-30 | 2021-07-27 | 杭州渗源环境科技有限公司 | Electroosmosis dehydration electrical parameter monitoring system and monitoring method thereof |
| CN114720813A (en) * | 2022-03-08 | 2022-07-08 | 昆明理工大学 | Deep well non-coal mine underground traction net protection method and system |
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