CN117728359A - Method for preventing override trip of power distribution system - Google Patents
Method for preventing override trip of power distribution system Download PDFInfo
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Abstract
The invention belongs to the technical field of power distribution systems, and discloses a method for preventing override tripping of a power distribution system, which is characterized in that override tripping protection modules are embedded into relay protection devices, DTU devices, FTU devices and override tripping protection module devices of all power distribution lines based on a distributed network protection technology, each override tripping protection module carries out independent override protection judgment, and particularly after the override tripping protection module of any power distribution line node detects a fault signal of the power distribution line, the override tripping protection module sends a 1-level locking signal to the upper level override tripping protection module to prevent the upper level override tripping protection module from tripping so as to enlarge the fault range; meanwhile, the override trip prevention protection module dynamically adjusts the trip delay according to whether the override trip prevention protection module receives a locking signal from a lower level override trip prevention protection module or not and according to the level of the received locking signal, thereby realizing selective trip and effectively solving override trip of a power distribution system.
Description
Technical Field
The invention belongs to the technical field of power distribution systems, and particularly relates to a method for preventing override trip of a power distribution system.
Background
The distribution network has wide quantity, complex grid structure and higher fault occurrence rate, more than 90% of faults of the power system are generated in the distribution network according to statistics, and along with the development of intelligent construction of the distribution network in China, higher requirements are also put forward on the reliability of the distribution network, but the total protection time difference between a power substation feed-out line cabinet and a power distribution terminal is very small, the number of stages of the distribution network is very large, so that the selectivity of short-circuit protection of the distribution network cannot be realized in a time-level difference mode, and the problem of override trip often occurs when faults occur; override trip means: when the power distribution system fails, the switch beyond the failed line also trips and fails, so that the non-failed line fails, and the influence range of the failed power failure is enlarged. Therefore, the method and the device effectively prevent the override trip of the power distribution system and have important significance for the power distribution reliability of the power distribution system.
At present, the main method for solving the problem of override trip prevention of a power distribution system is as follows: the optical fiber longitudinal difference is prevented from exceeding the level trip, and the centralized discrimination is prevented from exceeding the level trip, and specifically comprises the following steps:
(1) Level difference protection against override trip:
the short-circuit protection of the outgoing line circuit breaker of the substation is usually set with a protection tripping delay of 0.3S-0.5S, and the circuit breakers at all levels along the line realize the selectivity of protection action through the cooperation of time level differences.
(2) Differential protection against override trip:
the optical fiber longitudinal differential protection is configured at each level of the switch of the distribution line, the protection device communicates through the optical fiber and judges whether the fault occurs on the inner side or the outer side of the line, when the fault occurs on the outer side of the line, the optical fiber longitudinal differential protection does not act, and when the fault occurs on the inner side, the optical fiber longitudinal differential protection acts, but because the operation mode of the distribution line is complex, for example: single-inlet-wire multi-outlet, single-bus double-power supply, double-bus parallel operation and the like, the differential protection cannot realize automatic adaptation, and the reliability cannot be ensured.
(3) Centralized override trip prevention of the master station:
the power distribution main station establishes communication with the intelligent power distribution terminal in a wired or wireless mode, fault information detected by the intelligent terminal is uploaded to the power distribution main station, the power distribution main station determines a fault position according to a circuit cascading relation and sends a tripping instruction, and selective fault removal is achieved. Once the power distribution main station fails, the whole power distribution area can lose the protection against override trip, and the reliability can not be guaranteed.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention provides a method for preventing the override trip of a power distribution system, which is a step-by-step locking and dynamic adjustment of trip delay, and can effectively solve the override trip problem of the power distribution system.
The technical scheme adopted by the invention is as follows:
the method is applied to a distribution line, and for any n-level distribution electric cascade line in the distribution line, the method is formed by connecting n groups of protection units in series, each group is formed by connecting m protection units in parallel, each protection unit is embedded into an override trip prevention protection module, wherein n is a natural number, and n is more than or equal to 2; each protection unit is connected in series through a communication line, and each override trip prevention protection module performs independent override protection discrimination;
for any override trip protection module Fi, wherein Fi e (1, 2 … n), the following steps are performed:
s1.1, the override trip prevention protection module Fi detects power transmission information of an outgoing line side of a power distribution line in real time, judges whether a cascading line of the power distribution system fails or not based on the power transmission information, and if not, circularly executes the step; if yes, executing S1.2;
s1.2, starting from the moment of detecting the fault of the distribution line, executing the following two steps in parallel:
step 1: the override trip prevention protection module Fi sends a 1-level locking signal to the override trip prevention protection modules Fi+1 (1), fi+1 (2) and Fi+1 (k) of adjacent upper levels; wherein, the transmission time of the locking signal is ts;
step 2: the anti-override trip protection module Fi reads the set primary protection delay Tset0, then detects whether the self receives locking signals sent by adjacent lower-level anti-override trip protection modules Fi-1 (1) and Fi-1 (2) and Fi-1 (j) within the primary protection delay Tset0, and if the locking signals are not received, S1.3 is executed; if so, executing S1.4;
s1.3, indicating that a power distribution node where the override trip prevention protection module Fi is located is a primary power distribution fault node, judging whether the fault duration exceeds primary protection delay Tset0 or not by the override trip prevention protection module Fi, and executing S2 if the fault duration exceeds the primary protection delay Tset 0; otherwise, executing S3;
s1.4, the override trip prevention protection module Fi judges the level of the received locking signal, and the power distribution node where the override trip prevention protection module Fi is positioned is an x+1 level power distribution fault node if the level is assumed to be an x-level locking signal; then, the following two steps are performed in parallel:
step 1: the override trip prevention protection module Fi sends an x+1 level locking signal to the override trip prevention protection modules Fi+1 (1), fi+1 (2) and Fi+1 (k) of adjacent upper levels;
step 2: the override trip prevention protection module Fi dynamically adjusts the protection delay to an x-level protection delay Tsetx corresponding to the x-level locking signal; then, the override trip prevention protection module Fi detects whether the override trip prevention protection module Fi receives locking signals sent by adjacent lower level override trip prevention protection modules Fi-1 (1) and Fi-1 (2) and Fi-1 (j) within the time of the x-level protection delay Tsetx, and if the locking signals are not received, S1.5 is executed; if so, returning to S1.4;
s1.5, the override trip prevention protection module Fi judges whether the fault duration exceeds the x-level protection delay Tsetx, and if so, S2 is executed; otherwise, executing S3;
s2, the override trip prevention protection module Fi performs local protection, sends out a control signal, immediately trips a protection unit Fi, cuts off a fault line and sends out a trip alarm signal;
s3, the override trip prevention protection module Fi sends unlocking signals to the upper level override trip prevention protection modules Fi+1 (1), fi+1 (2) and Fi+1 (k);
the signal transmission time for transmitting the locking signal between two adjacent override trip prevention protection modules is set as ts;
the tripping action time of each protection unit is the same, and is delta t;
the reliability coefficient is set as w and is constant;
then: for the above-mentioned primary protection delay Tset0, secondary protection delay Tset1 … (n-1) and the secondary protection delay Tset (n-2), the following conditions should be satisfied:
Tset0>ts；
ts+Tset1+w>Tset0+△t；
ts+Tset2+w>Tset1+△t；
…
ts+Tset(n-1)+w>Tset(n-2)+△t。
preferably, in S1.1, the power transmission information on the outlet side of the distribution line includes a voltage value or a current value;
judging whether the cascade circuit of the power distribution system has faults or not, specifically: and judging whether the cascade circuit of the power distribution system has short circuit fault or electric leakage fault.
Preferably, when the override trip protection module Fi detects the current value of the outlet side of the power distribution line in real time and judges whether the cascade line of the power distribution system has a short circuit fault, the following method is adopted to judge:
the override trip prevention protection module Fi detects the current value of the outlet side of the power distribution line in real time, judges whether the abrupt change value between the current value obtained by sampling at the current moment and the current value obtained by sampling at the previous moment is larger than a set threshold value, and directly obtains that the cascading line of the power distribution system has no short circuit fault if the abrupt change value is not larger than the set threshold value; if the current value is larger than the current value, further calculating the current value obtained by sampling at the current moment to obtain a current effective value and a current phase angle; and then, based on the current effective value and the current phase angle, a conclusion is drawn whether the cascading lines of the power distribution system have short-circuit faults or not.
Preferably, in S3, the signal transmission time ts for transmitting the blocking signal between two adjacent override trip protection modules is less than 1 millisecond; the tripping action time Deltat between the protection units is 70-80 milliseconds; the reliability coefficient w is 10 milliseconds.
Preferably, the primary protection delay Tset0 is 3 milliseconds; the secondary protection delay Tset1 is 100 milliseconds; the three stage protection delay Tset2 is 200 milliseconds.
Preferably, the protection unit is one of a relay protection device, a DTU device, an FTU device and an override trip prevention protection module device, and each protection unit is embedded into the override trip prevention protection module.
Preferably, each protection unit selects either wired communication or wireless communication when connected in series through a communication line.
The method for preventing the override trip of the power distribution system has the following advantages:
the method for preventing the override trip of the power distribution system provided by the invention has the advantages that each level of protection switch is used for locking the upper level switch step by step, and the protection trip delay of the current level switch is dynamically adjusted, so that the override trip is effectively prevented, and the backup protection of the current level switch during failure override or communication link interruption is realized.
Drawings
FIG. 1 is a schematic diagram of a wiring scheme for preventing override trip of a power distribution system provided by the present invention;
FIG. 2 is a diagram of a communication circuit for preventing override trip of a power distribution system provided by the present invention;
FIG. 3 is a schematic illustration of a cascading circuit of a power distribution system;
fig. 4 is a diagram of a main program of operation of the override trip protection module provided by the invention;
FIG. 5 is a flow chart of data sampling provided by the present invention;
fig. 6 is a flowchart of an override trip prevention method in setting a 3-level fault trip time according to the present invention.
Detailed Description
The invention is described in detail below with reference to the attached drawing figures:
referring to fig. 1, the invention provides a method for preventing override trip of a power distribution system, which is basically implemented according to the following principle:
designing an override trip prevention protection module, embedding the override trip prevention protection module into protection units of all distribution lines of a distribution system, and independently judging override trip prevention protection by each override trip prevention module, wherein the override trip prevention module specifically comprises the following components: after the fault signal of the distribution line is detected by the override trip prevention protection module Fi at any distribution node position, a 1-level locking signal is sent to the upper-level override prevention protection module Fi+1 (1), fi+1 (2) and Fi+1 (k) by the override trip prevention protection module Fi, so that the upper-level override trip prevention protection module Fi+1 (1), fi+1 (2) and Fi+1 (k) are prevented from tripping to enlarge the fault range; meanwhile, the trip delay of the override trip prevention protection module Fi is dynamically adjusted, namely: according to whether the locking signals from the lower-level override trip prevention protection modules Fi-1 (1) and Fi-1 (2) and according to the level of the received locking signals, the trip delay is dynamically adjusted, so that selective trip is realized, and override trip is avoided.
Specifically, referring to fig. 2, the protection units are relay protection devices, DTU devices or FTU devices, and the override trip prevention protection modules are respectively embedded in the protection units and execute the method by using relays in the protection units; or the protection unit independently configures a main circuit switching element for the override trip prevention protection module device to execute the method; and the same type of distribution system only selects one of the distribution systems, for example, a city power supply system or a ship power supply system in a certain area respectively selects different protection units.
For any n-level distribution electric cascade circuit in the distribution circuit, the n-level distribution electric cascade circuit is formed by connecting n groups of protection units in series, each group is formed by connecting m protection units in parallel, the protection units are one of a relay protection device, a DTU device, an FTU device and an override trip prevention protection module device, the same type of distribution system is only one type, each protection unit is embedded into the override trip prevention protection module, wherein n is a natural number, and n is more than or equal to 2;
each protection unit is connected in series through a communication line, and each override trip prevention protection module performs independent override protection discrimination;
specifically, for any override trip protection module Fi, wherein Fi e (1, 2 … n), the following steps are executed:
s1.1, the override trip prevention protection module Fi detects power transmission information of an outgoing line side of a power distribution line in real time, judges whether a cascading line of the power distribution system fails or not based on the power transmission information, and if not, circularly executes the step; if yes, executing S1.2;
in the concrete implementation, whether the cascading circuit of the power distribution system fails or not can be judged by detecting the voltage value of the outlet side of the power distribution circuit; and whether the cascading circuit of the power distribution system fails or not can be judged by detecting the current value of the outlet side of the power distribution circuit. The specific detection modes are very various, and according to actual requirements, whether the power distribution system cascade circuit has short-circuit faults or not can be detected, and whether the power distribution system cascade circuit has leakage faults or not can also be detected.
As a specific implementation manner, when the override trip protection module Fi detects the current value of the outlet side of the power distribution line in real time and judges whether the cascade line of the power distribution system has a short circuit fault, the following method is adopted to judge:
the override trip prevention protection module Fi detects the current value of the outlet side of the power distribution line in real time, judges whether the abrupt change value between the current value obtained by sampling at the current moment and the current value obtained by sampling at the previous moment is larger than a set threshold value, and directly obtains that the cascading line of the power distribution system has no short circuit fault if the abrupt change value is not larger than the set threshold value; if the current value is larger than the current value, further calculating the current value obtained by sampling at the current moment to obtain a current effective value and a current phase angle; and then, based on the current effective value and the current phase angle, a conclusion is drawn whether the cascading lines of the power distribution system have short-circuit faults or not.
S1.2, when the override trip protection module Fi detects that the distribution line breaks down, the following two steps are executed in parallel from the moment of detecting that the distribution line breaks down:
step 1: the override trip prevention protection module Fi sends a 1-level locking signal to the override trip prevention protection modules Fi+1 (1), fi+1 (2) and Fi+1 (k) of adjacent upper levels; wherein, the transmission time of the locking signal is ts;
step 2: the protection module Fi is used for reading the set primary protection delay Tset0, detecting whether the protection module Fi receives blocking signals sent by adjacent lower-stage protection modules Fi-1 (1) and Fi-1 (2) and Fi-1 (j) within the primary protection delay Tset0, and executing S1.3 if the blocking signals are not received; if so, executing S1.4;
s1.3, indicating that a power distribution node where the override trip prevention protection module Fi is located is a primary power distribution fault node, judging whether the fault duration exceeds primary protection delay Tset0 or not by the override trip prevention protection module Fi, and executing S2 if the fault duration exceeds the primary protection delay Tset 0; otherwise, executing S3;
s1.4, judging the level of the received blocking signal by the override trip prevention protection module Fi, setting the level as an x-level blocking signal, and indicating that a power distribution node where the override trip prevention protection module Fi is positioned is an x+1-level power distribution fault node; then, the following two steps are performed in parallel:
step 1: the override trip prevention protection module Fi sends an x+1 level locking signal to the override trip prevention protection modules Fi+1 (1), fi+1 (2) and Fi+1 (k) of adjacent upper levels;
step 2: the override trip prevention protection module Fi dynamically adjusts the protection delay to an x-level protection delay Tsetx corresponding to the x-level locking signal; then, the override trip prevention protection module Fi detects whether the override trip prevention protection module Fi receives locking signals sent by adjacent lower level override trip prevention protection modules Fi-1 (1) and Fi-1 (2) and Fi-1 (j) within the time of the x-level protection delay Tsetx, and if the locking signals are not received, S1.5 is executed; if so, returning to S1.4;
s1.5, the override trip prevention protection module Fi judges whether the fault duration exceeds the x-level protection delay Tsetx, if so, S2 is executed, and the trip is performed; otherwise, executing S3;
s2, the override trip prevention protection module Fi performs local protection, controls the protection unit Fi to trip immediately, cuts off a fault line and sends out a trip alarm signal;
s3, indicating that faults are eliminated in the x-level protection delay Tsetx, wherein the override trip prevention protection module Fi sends unlocking signals to the upper level override trip prevention protection modules Fi+1 (1), fi+1 (2) and Fi+1 (k);
the signal transmission time for transmitting the locking signal between two adjacent override trip prevention protection modules is set as ts;
the action time of tripping action of each relay protection device, DTU device, FTU device and override trip prevention protection module device is the same as deltat;
the reliability coefficient is set as w and is constant;
then: for the above-mentioned primary protection delay Tset0, secondary protection delay Tset1 … (n-1) and the secondary protection delay Tset (n-2), the following conditions should be satisfied:
Tset0>ts；
ts+Tset1+w>Tset0+△t；
ts+Tset2+w>Tset1+△t；
…
ts+Tset(n-1)+w>Tset(n-2)+△t。
for easy understanding, the specific process of the method for preventing the override trip of the power distribution system provided by the invention is described by taking an override trip prevention project as an example;
first, the initial parameters are set as: ts is less than 1 millisecond; Δt is 80 milliseconds; the reliability coefficient w is 10 milliseconds. The primary protection delay Tset0 is 3 milliseconds; the secondary protection delay Tset1 is 100 milliseconds; the three stage protection delay Tset2 is 200 milliseconds.
As shown in fig. 3, which is a specific schematic diagram of a cascading circuit of a power distribution system, in order from the upper level to the lower level, a protection switch 302, a protection switch 301, a protection switch 202, a protection switch 201, and a protection switch 102 form a cascading circuit of the power distribution system, and an override trip protection module respectively connected to the protection switch 302, the protection switch 301, the protection switch 202, the protection switch 201, and the protection switch 102 is recorded as: an override trip protection module 302, an override trip protection module 301, an override trip protection module 202, an override trip protection module 201, and an override trip protection module 102.
For simplicity of description, the override trip protection module is abbreviated as FYJ;
FYJ302, FYJ, FYJ, 202, FYJ201 and FYJ102 respectively detect the current condition of the respective outgoing line side in real time, and considering the limit condition, when the line end, i.e. the outgoing line side of the protection switch 302 has a short circuit fault, the protection switches of all the cascade lines (302, 301, 202, 201, 102) almost simultaneously flow short circuit currents, so that each override trip protection module almost simultaneously detects that the outgoing line side of the distribution node where it is located has a short circuit fault, and from the moment when the short circuit fault is detected, assuming that t=0 moment, each override trip protection module simultaneously performs the following operations:
step 1: FYJ302 sends a level 1 lock signal to FYJ with a signal transmission time <1 millisecond;
meanwhile, FYJ sends a level 1 lock signal to FYJ, signal transmission time <1 millisecond;
meanwhile, FYJ202 sends a level 1 lock signal to FYJ, signal transmission time <1 millisecond;
meanwhile, FYJ201 sends a level 1 lock signal to FYJ, signal transmission time <1 millisecond;
step 2: for FYJ, while sending a level 1 latch signal to FYJ301, detecting whether the fault has cleared within tset0=3 milliseconds, if so, sending a notification message to FYJ301 to unlatch the latch; otherwise, when reaching 3 milliseconds, tripping, cutting off the fault line and sending out a tripping alarm signal; if the trip action time is normally within 80 milliseconds, the reliability factor is set to 10 milliseconds: in the time of tset1=100 milliseconds, FYJ302 can successfully cut off the fault line, and then the whole power distribution line is recovered to the normal power distribution condition, and the fault is relieved; however, there are also cases where FYJ302 fails to trip, and the fault is not relieved;
for FYJ, while sending a level 1 latching signal to FYJ202, detecting if a latching signal from FYJ302 was received within a time of tset0=3 milliseconds, if no communication failure occurs, FYJ301 would normally be able to receive a level 1 latching signal from FYJ302 within a time of 3 milliseconds, at which point FYJ301 would not trip and dynamically adjust the protection delay to tset1=100 milliseconds, since the signal transmission time between adjacent distribution nodes is <1 millisecond; then, whether the fault is eliminated within 100 milliseconds is judged, and if the fault is eliminated, a notification message of releasing the locking signal is sent to FYJ 202; otherwise, when reaching 100 milliseconds, tripping, cutting off the fault line and sending out a tripping alarm signal; this condition refers to the case of FYJ302 trip failure;
for FYJ202, while sending a level 1 latching signal to FYJ201, detecting if a latching signal from FYJ is received within a time of tset0=3 milliseconds, if no communication failure occurs, FYJ202 is able to normally receive a level 1 latching signal from FYJ301 within a time of 3 milliseconds, at which point FYJ202 does not trip and dynamically adjusts the protection delay to tset1=100 milliseconds, since the signal transmission time between adjacent distribution nodes is <1 millisecond; then, it is determined whether the level 2 latch signal from FYJ301 can be received within 100 ms, and in normal cases, FYJ is not tripped at this time, and the protection delay is dynamically adjusted to tset2=200 ms; then, it is judged whether or not the fault is eliminated within 200 ms, and if so, a notification message of releasing the latch signal is sent to FYJ 201; otherwise, when reaching 200 milliseconds, tripping, cutting off the fault line and sending out a tripping alarm signal; this refers to the case where both FYJ and FYJ are trip failed.
The working principle of other override trip prevention protection modules is the same as that described above, and will not be described again here.
It should be emphasized that, for each override trip protection module, in the working process, as long as a message that the fault has been successfully relieved is detected at any time, or a notification message of a unblocking signal sent by a lower override trip protection module is received, it indicates that the power distribution line has been recovered to be normal at the time, and the current override trip protection module does not need to trip, so that the unblocking is performed.
Therefore, the method for preventing the override trip of the power distribution system is a step-by-step locking and dynamic tripping delay adjustment method, and each step of protection switch locks the upper step of switch step by step and dynamically adjusts the protection tripping delay of the current step of switch, so that the override trip is effectively prevented, and the backup protection of the current step of switch during failure rejection or communication link interruption is realized.
In practical application, the override trip prevention protection module provided by the invention is a software program, is designed based on a nucleous real-time operating system, creates an override trip prevention protection advanced interrupt task and other middle and advanced interrupt tasks after the program is run, initializes memory data and performs device health check (self-checking), and starts each interrupt task program to complete related functions in parallel after the self-checking is successful, as shown in fig. 4, and is a main program diagram for the override trip prevention protection module; as shown in fig. 5, a data sampling flow chart; the data sampling frequency in the program is 3kHz, and the reading of the A/D sampling result, the fault information processing, the protection discrimination of the override trip prevention, the communication and the like are all completed in the corresponding interrupt task.
The sample interrupt task is performed every 0.333ms (60 points/period). In the task, A/D conversion is started, the A/D conversion result is read and stored in RAM, and the sampled data is subjected to necessary pre-filtering treatment, and 15-period sampling values are circularly stored for tasks such as fault detection, override judgment and the like.
The fault detection start-up procedure is located in the sample interrupt procedure and is therefore performed every 0.333 ms.
The fault detection program judges whether the short-circuit protection is started or not according to the phase current difference mutation value, namely:
Δi (k) = |i (k) +i (k-N/2) | -i (k-N/2) +i (k-N) | by adopting a two-half cycle comparison algorithm, the data window is shorter, and unbalanced current generated by frequency deviation can be compensated. After the short-circuit fault is detected, a short-circuit fault starting mark is set.
In the advanced interruption, the anti-override protection judging program is started once in 50 mu s, after the program detects a short-circuit fault starting sign, a 1-level locking signal is immediately sent to an upper-level protection switch in an optical fiber communication mode, meanwhile, whether a locking signal is input to a lower-level switch is detected, if the fault continuously exists for Tset0 time, the switch immediately trips, and a fault line is cut off; if the fault continuously exists the Tset0 time and receives the blocking signal sent by the lower-stage switch, the level of the blocking signal is judged firstly, if the fault continuously exists the Tset0 time, the switch sends a 2-stage blocking signal to the upper-stage switch, meanwhile, the current quick-break protection delay of the switch is adjusted to be Tset1, the fault continuously exists the Tset1 time and then is tripped, and a fault line is cut off; if the fault duration time Tset1 is within the time period of receiving the 2-level locking signal sent by the lower-level switch, the switch sends the 3-level locking signal to the upper-level switch, and meanwhile, the current quick-break protection delay of the switch is adjusted to be Tset2, wherein in the embodiment, the device sets 3-level fault tripping time, protects tripping after the fault duration time Tset2, and cuts off a fault line. As shown in fig. 6, a flow chart of an override trip prevention method when setting a 3-level fault trip time is shown.
Therefore, each level switch dynamically adjusts the protection tripping time of the switch to be Tset0, tset1 or Tset2 according to the received blocking signal, and simultaneously dynamically adjusts the level of sending the blocking signal to the level switch to be 1 level, 2 level or 3 level. In this way, each stage of protection switch is locked with the upper stage switch step by step, and the protection tripping delay of the present stage of switch is dynamically adjusted, so that not only is the override tripping prevented effectively, but also the backup protection of the present stage of switch during failure refusal or communication link interruption is realized; the anti-override protection discrimination program is started once within 50 mu s, so that the anti-override protection logic discrimination can be completed within 100 mu s, and the anti-override protection discrimination of the whole system can be completed within 3ms by considering the optical fiber transmission delay (limit delay 1 ms) and the optical fiber switch delay (limit delay 1 ms), so that the power supply reliability is greatly improved.
In summary, compared with the optical fiber longitudinal differential method in the prior art, the method for preventing the override trip of the power distribution system has the following advantages in solving the override trip problem of the power distribution system:
(1) The method is designed into an override trip prevention protection module, is embedded into each level of protection units, realizes on-site protection and override prevention judgment, and has the advantages of quicker relay protection action and shorter override prevention judgment time.
(2) The anti-override trip protection modules of the upper and lower protection units automatically form the minimum anti-override network unit and jointly form an anti-override trip network of the whole system, so that network interruption or network blockage of an independent area does not influence the anti-override trip protection function of the whole system, the anti-override trip power distribution network is stronger, and the power supply is more reliable.
(3) The anti-override protection program modules of the protection units at all levels are universal and are not changed due to different power distribution modes, so that the anti-override relay protection program is more stable and higher in reliability.
(4) Therefore, the method for locking step by step and dynamically adjusting the tripping delay can thoroughly solve the problem of override tripping of the power distribution system, avoid large-area and long-time power failure, and improve the power supply reliability.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which is also intended to be covered by the present invention.
Claims (7)
1. The method is applied to a distribution line, and for any n-level distribution electric cascade line in the distribution line, the method is formed by connecting n groups of protection units in series, each group is formed by connecting m protection units in parallel, each protection unit is embedded into an override trip prevention protection module, wherein n is a natural number, and n is more than or equal to 2;
each protection unit is connected in series through a communication line, and each override trip prevention protection module performs independent override protection discrimination;
the protection method is characterized in that for any override trip prevention protection module Fi, the following steps are executed for Fi E (1, 2 … n):
s1.1, the override trip prevention protection module Fi detects power transmission information of an outgoing line side of a power distribution line in real time, judges whether a cascading line of the power distribution system fails or not based on the power transmission information, and if not, circularly executes the step; if yes, executing S1.2;
s1.2, starting from the moment of detecting the fault of the distribution line, executing the following two steps in parallel:
step 1: the override trip prevention protection module Fi sends a 1-level locking signal to the override trip prevention protection modules Fi+1 (1), fi+1 (2) and Fi+1 (k) of adjacent upper levels; wherein, the transmission time of the locking signal is ts;
step 2: the anti-override trip protection module Fi reads the set primary protection delay Tset0, then detects whether the self receives locking signals sent by adjacent lower-level anti-override trip protection modules Fi-1 (1) and Fi-1 (2) and Fi-1 (j) within the primary protection delay Tset0, and if the locking signals are not received, S1.3 is executed; if so, executing S1.4;
s1.3, indicating that a power distribution node where the override trip prevention protection module Fi is located is a primary power distribution fault node, judging whether the fault duration exceeds primary protection delay Tset0 or not by the override trip prevention protection module Fi, and executing S2 if the fault duration exceeds the primary protection delay Tset 0; otherwise, executing S3;
s1.4, the override trip prevention protection module Fi judges the level of the received locking signal, and the power distribution node where the override trip prevention protection module Fi is positioned is an x+1 level power distribution fault node if the level is assumed to be an x-level locking signal; then, the following two steps are performed in parallel:
step 1: the override trip prevention protection module Fi sends an x+1 level locking signal to the override trip prevention protection modules Fi+1 (1), fi+1 (2) and Fi+1 (k) of adjacent upper levels;
step 2: the override trip prevention protection module Fi dynamically adjusts the protection delay to an x-level protection delay Tsetx corresponding to the x-level locking signal; then, the override trip prevention protection module Fi detects whether the override trip prevention protection module Fi receives locking signals sent by adjacent lower level override trip prevention protection modules Fi-1 (1) and Fi-1 (2) and Fi-1 (j) within the time of the x-level protection delay Tsetx, and if the locking signals are not received, S1.5 is executed; if so, returning to S1.4;
s1.5, the override trip prevention protection module Fi judges whether the fault duration exceeds the x-level protection delay Tsetx, and if so, S2 is executed; otherwise, executing S3;
s2, the override trip prevention protection module Fi performs local protection, sends out a control signal, immediately trips a protection unit Fi, cuts off a fault line and sends out a trip alarm signal;
s3, the override trip prevention protection module Fi sends unlocking signals to the upper level override trip prevention protection modules Fi+1 (1), fi+1 (2) and Fi+1 (k);
the signal transmission time for transmitting the locking signal between two adjacent override trip prevention protection modules is set as ts;
the tripping action time of each protection unit is the same, and is delta t;
the reliability coefficient is set as w and is constant;
then: for the above-mentioned primary protection delay Tset0, secondary protection delay Tset1 … (n-1) and the secondary protection delay Tset (n-2), the following conditions should be satisfied:
Tset0>ts；
ts+Tset1+w>Tset0+△t；
ts+Tset2+w>Tset1+△t；
…
ts+Tset(n-1)+w>Tset(n-2)+△t。
2. the method of claim 1, wherein in step S1.1, the power transmission information on the outlet side of the power distribution line includes a voltage value or a current value;
judging whether the cascade circuit of the power distribution system has faults or not, specifically: and judging whether the cascade circuit of the power distribution system has short circuit fault or electric leakage fault.
3. The method for preventing override trip of power distribution system according to claim 2, wherein when the override trip prevention protection module Fi detects the current value of the outgoing line side of the power distribution line in real time and judges whether the cascade line of the power distribution system has a short circuit fault, the following method is adopted to judge:
the override trip prevention protection module Fi detects the current value of the outlet side of the power distribution line in real time, judges whether the abrupt change value between the current value obtained by sampling at the current moment and the current value obtained by sampling at the previous moment is larger than a set threshold value, and directly obtains that the cascading line of the power distribution system has no short circuit fault if the abrupt change value is not larger than the set threshold value; if the current value is larger than the current value, further calculating the current value obtained by sampling at the current moment to obtain a current effective value and a current phase angle; and then, based on the current effective value and the current phase angle, a conclusion is drawn whether the cascading lines of the power distribution system have short-circuit faults or not.
4. The method of claim 1, wherein in step S3, a signal transmission time ts for transmitting a blocking signal between two adjacent override trip protection modules is less than 1 millisecond; the tripping action time Deltat between the protection units is 70-80 milliseconds; the reliability coefficient w is 10 milliseconds.
5. A method of preventing override tripping in a power distribution system as defined in claim 4, wherein the primary protection delay Tset0 is 3 milliseconds; the secondary protection delay Tset1 is 100 milliseconds; the three stage protection delay Tset2 is 200 milliseconds.
6. The method of claim 1, wherein the protection units are one of relay protection devices, DTU devices, FTU devices, and override trip protection module devices, each of the protection units embedded with an override trip protection module.
7. A method of preventing override tripping in a power distribution system as defined in claim 1, wherein the protection unit is in wired or wireless communication.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311483713.3A CN117728359A (en) | 2023-11-08 | 2023-11-08 | Method for preventing override trip of power distribution system |
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