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Reprinted from alumni of the user at 23:34 on September 27, 2010 Reading (loading. ..) Comments (0) Category: Professional reproduced
Glossary:
1, loss of field: is a generator loss of field operation, because some of the excitation circuit fault caused by the excitation current interruption.
2, zero sequence current: power system occur at any point in single or two ground short circuit fault, the system will generate zero sequence current. At this point, the point of failure in the ground there will be a zero sequence voltage, this voltage will be produced under zero sequence current, zero sequence current through the earth from the point of failure of electrical equipment to the neutral ground for the circuit to return to the unique point of failure a reflection of the ground fault current.
3, high-frequency current: is the high-frequency protection circuit in the high-frequency signal current. This current is compared with the current frequency, named after, the frequency change of the current 50 times per minute to minute, while the high-frequency current over each 35KHZ wonderful change, and now the system is generally used for high-frequency 35 ~ 500KHZ.
4, breakdown voltage: the role of insulation in the voltage, the time-out when a certain threshold, sudden loss of insulation dielectric discharge occurs is called the breakdown, the critical value called the breakdown voltage.
5, to help increase current: current is affected by the distance to help protect the right to work an additional current. Because in many cases, the protection of the link between the point of failure to install in the other branches of current, the power will supply additional short-circuit current, so the current through the fault line protection device is greater than the current flows. The current and called to help increase current.
6, capacitor voltage transformer: the use of capacitive divider model for voltage conversion of the voltage transformer, said capacitor voltage transformer.
7, high-frequency processing equipment: high-frequency traps, coupling capacitors, filters and high-frequency cables and other links referred to as high frequency high voltage line processing equipment.
8, power distribution equipment: all kinds of electrical equipment in accordance with certain requirements of a link made to indicate the construction of energy production, transmission and distribution of electrical building, a power distribution unit.
Q & A Question:
1, the original computer relay protection and what constitutes the difference?
main difference is that the protection of the original input is the current, voltage signal, direct comparison between the analog processing and analog devices to a given treatment resistance moment are compared. The computer can only be number operations or logic operations. Therefore, the first claim of the analog input current and voltage values of the moment bit discrete digital transformation, and then the computer can be sent to the central processor, the required computing algorithms and procedures, and the result of the operation at any time with the figures given comparison, the last to judge whether the trip.
2, zero sequence current protection is the protection of each section of how to divide? section of zero sequence current I
escaped through the ground fault circuit protection of the end of the maximum zero sequence current setting; can not protect the full length of line, but should not be protected line length of less than 15% to 20%; zero Section II General protection order the full length of line, and I extend to the adjacent line segments within and with the cooperation. Section III is a zero-sequence I, II section of the reserve section, and with the adjacent line.
3, what is the acceleration after the reclosing?
When the line fails to protect the value of action by setting the line switch is turned off, immediately reclosing action. If the transient fault, switch off the line after the fault disappears, coincidence success, to restore power lines; if a permanent fault, coincidence, the protection element is out of time, it becomes 0 second trip, this is the reclosing Failure is not accelerate after the disappearance of action trip, trip cut point of failure.
4, misuse isolation switch should I do?
(1)'re wrong isolating switch, the switch has just left the static arc contact has occurred, then immediately closed, can arc to avoid the accident, if switch has been fully opened, the pull of the knife must not be mistakenly re-closed; (2) pull the wrong isolating switch, even if the combined fault, even when in the closing arc, was not allowed to re-opened, because with a load Knife may cause short-circuit three-phase arc.
5, what is R, L, C parallel resonance?
resistors, inductors and capacitors in parallel circuit, the frequency of the sinusoidal power supply in a certain role, the emergence of the circuit voltage and total current phase, the entire circuit resistance was the special status which is called parallel resonance.
6, emitter of the main features of that?
larger input resistance, low output resistance, voltage amplification factor is approximately equal to 1, but less than 1, the input voltage and output voltage.
7, protective device complies with the conditions may assess the positioning of a class of device?
a class of devices all protective devices, the technology in good condition, safe operation of the system to fully meet the performance requirements and comply with the following main conditions: (1) to protect screen, relays, components,
timberland boots sale, ancillary equipment and secondary circuit without flaws. (2) The principle of the device, wiring and setting right in line with relevant provisions of the Ordinance requirements and anti-accident measures. (3) drawings are complete and realistic. (4) running in good condition.
8, the checks on the control switch and its content?
check on the control switch includes: (1) housing clean and free of grease, intact. (2) The installation should be firm,
mens timberland boots, the operation is not active. (3) closures sealed well. (4) lug connection should be firm, not loose, no rust. (5) Turn the flexibility, the correct position, contact. (6) Open the closures, shine a flashlight with the inspection, the internal should be clean, grease does not dry, the contact point without burning. Pressure test stick contact with insulating film, the pressure should be good.
9, transformer differential protection of transformer no-load into the private check what time?
transformer differential protection, the newly installed transformer must be done 5 times rated voltage no-load test. Put in for no-load before the secondary wiring should be checked and make sure correct. No-load test should be put into a large power transformer and low voltage side to side, it is hungry because the system impedance and the transformer leakage reactance can play the role of limit inrush current,
timberland uk, and a large supply side of the system impedance is small, and generally low-voltage transformer winding around the inside , low leakage reactance, it is in large supply and low voltage side of the input inrush current when larger. In the study,
timberland kids, protection should not be the first action, otherwise the relay operating current should be increased.
10, in the dismantled second line, what measures should be taken?
dismantled the second line, you must make a record; recovery. Should be recorded in the record books on the cancellation. The second line changes more, should the head bolts on each line card. Dismantled, or the laying of the second cable, the cable should also along the first corner of the end of its components at the bolt and cross-licensing
11, gas protection measures against accidents What are the requirements?
(1) will float to the next gas relay flapper, the contact to vertical in order to improve the reliability of the heavy gas action. (2) To prevent gas leakage due to short-circuit relay, should be at its end and the cable terminal wire terminal box measures taken by rain. (3) Gas and oil relay Lead wire should be used. (4) hungry, ah, is the relay pinout and cables should be connected to the cable lead wires were inside the terminal.
12, transformer installed in the general principles?
(1) Defense internal short circuit the transformer iron shell surface of lower gas and oil protection. (2) Defense Lead the phase coil and the transformer short-circuit, large ground current power leads to the side of the ground side of the coil short-circuit and short circuit between coils longitudinal differential protection or Current Protection. (3) defense and the transformer for the external gas phase short-circuit protection and backup of longitudinal differential protection over current protection (or composite voltage start over current protection, or negative sequence current protection). (4) large ground defense of external ground short-circuit current network zero sequence current protection. (5) defense symmetric overload protection overload.
13, the relay out and put into what is required?
out protection, you should exit the protection tripping plate, the protection of power after the withdrawal. Investment protection, operation and protection of exit in the reverse order.
14,10 kV transmission line protection of the general installation of what?
(1) phase short-circuit protection: the installation of two-stage single-supply circuit generally over-current protection, which Current Protection, definite time overcurrent protection. Dual power supply line installed with the direction or general direction of the current rate without protection and over-Current Protection. (2) ground fault protection: general non-selective insulation installed to monitor protection, zero sequence over-voltage protection, power directional protection.
15, negative feedback on performance amplifier What is the impact?
(1) lower magnification, (2) to improve the stability of the magnification, (3) improve the waveform distortion, (4) broadening the pass band , (5) changes in the amplifier input and output resistance.
16, non-sinusoidal currents cause?
non-sinusoidal current generation, can be a power supply, can also be a load. Usually have the following reasons: (1) There are several different circuits simultaneously sinusoidal electromotive force, or the interaction of AC and DC force, (2) the circuit with a non-sinusoidal electromotive force. (3) non-linear components in the circuit.
17,6 ~ 35kV power system connected to the relative voltage arrester, why lightning arrester according to the rated line voltage selection?
6 ~ 35kV system is a small ground short-circuit current system, under normal circumstances, the lightning is relatively under-voltage, but the single-phase ground fault occurs, the non-fault phase to ground voltage to rise to the line voltage, and The ground fault time allowed to exist at this time arrester should not be action. Therefore, the arrester rated voltage must use the rated line voltage rather than the rated phase voltage.
18, protection device meets the conditions are three types of devices can be classified as?
three types of equipment, protective devices or equipment failure, or poor technical performance and thus affect the safe operation of the system. If the main protection device one of the following conditions also named three types of equipment: (1) The protection does not meet the system requirements, the failure can cause system oscillation, the collapse of an accident or serious damage to the main point of equipment, of the. (2) does not meet the requirements of anti-accident measures. (3) for operating personnel to operate the connected pieces, handles, buttons, etc. with signs. (4), incomplete drawings, and does not conform to reality, (5) recorded a wave fault recorder can not in good condition or not in operation.
19, in the relay test, how to master the test environmental conditions?
test environment conditions, including temperature, relative humidity, and pressure in three aspects. These conditions affect not only the basic performance of the relay to be tested, and working conditions of the test equipment is also affected. Environmental conditions on the test requirements are as follows: (1) Temperature: 15 ~ 35 degrees (2) Humidity: 45 ~ 75% (3) air pressure: 660 ~ 780mmHg
20 in the choice of test instruments, it is necessary to grasp what principle?
(1) Select the object to be measured according to the type of instrument. First, the relay under test is a DC or AC, the choice of DC or AC meter instrument. (2) Based on the test line and the size of the measured impedance of the relay coil resistance selection instrument. (3) According to the measured size of the choice of appropriate instruments. (4) The use of the premises and working conditions of selected instruments.
21, newly installed after the completion of the protection device, the main acceptance of the project have?
acceptance of the project are as follows: (1) Electrical equipment and wiring on the measured parameters of complete and correct. (2) completion of all protective devices drawing realistic. (3) test setting value consistent with the requirements of notice. (4) inspection items and inspection and test results meet the provisions of the Ordinance and related regulations. (5) check the current transformer ratio and voltage characteristics, the secondary load to meet the error requirement. (6) Check the screen before the screen of the equipment tidy, good condition, good insulation circuit, marking complete correctly. (7) with a load current and voltage for acceptance tests to determine the transformer polarity, the transformation ratio and the loop is correct, determine direction, differential, distance, high-frequency components and other protective devices on the correctness of wiring.
22, in the normal operation of the current system of how to test a large ground zero sequence directional zero sequence voltage protection circuit?
zero-sequence directional protection to ensure the correct action to deal with zero-sequence directional zero sequence voltage protection circuit integrity checks. The method is to use the open delta connection voltage transformer secondary winding test leads for a small bus on the direction of the various sets of zero-sequence voltage protection are small bus YMN measure voltage 100V, is the normal.
23, in a small ground current system of radiating power in the single-phase ground fault occurs, the fault lines of current and non-fault line What is the difference?
fault line sending end of the measured zero-sequence capacitive current, equal to the other lines zero sequence currents and capacitance, and the flow of bus. Non-fault line the sender is the measured zero sequence current of the circuit relative to the non-fault capacitance current, and out of bus.
24, in large ground current system, why the time limit for protection action phase sequence protection than zero long-time action?
time the action is generally protected by the principle of tuning ladder. White protective action time, the direction by the user to supply a time limit for each level of protection increasing differential form,
timberland boots, and zero-sequence protection is the step-down transformers are mostly Y / wiring is shorted to ground when the low side, high side no zero sequence current, its action time users do not need to match low-voltage transformer. Therefore, the action of zero sequence protection phase protection than a short time.
25, what is the power system oscillations? Oscillation caused by the general reasons for what?
parallel operation of two systems or power plants out of sync the phenomenon known as oscillation. Oscillation caused by many reasons,
timberland boots uk, most of the time to failure due to excessive removal of the dynamic stability caused the destruction of the system in the weak links may also be due to misuse, or failure of generator loss of field trip, breaking a line or work equipment caused by oscillation.
26, where the modulator should meet several requirements?
(1) when the input DC signal Ui = 0, the output signal U0 = 0 (2) the amplitude of the output AC signal, the signal should be proportional to the size of DC, (3) When the polarity of the DC signal Ui changes , the output AC signal phase also changed.
27,35 kV neutral point grounding system, circuit configuration phase short-circuit protection principles?
configuration phase short-circuit protection principles are: (1) When using two-phase current protection, current transformer should be installed in two phases of the same name appears (eg A, C phase). (2) protection devices protection devices should be used far back way. (3) Power Plants will short-circuit bus, the main power supply bus or an important focal point for the user bus voltage is lower than the rated voltage of 50% to 60% should be quickly removed failure.
28, in the high-voltage power grid, high-frequency protection function?
in long-distance high-frequency high-voltage transmission line protection on the road, at any point on the protected circuit can malfunction of the instantaneous removal from both sides, which can improve power system stability and the success rate of reclosing.
29, a large ground current system, why the time limit for protection action phase sequence protection than zero long-time action?
time the action is generally protected by the principle of tuning ladder. White protective action time is the direction by the user to supply a time limit for each level of protection increasing poor form, and zero-sequence protection is the step-down transformers are mostly Y, d11 connection, when the low pressure side is shorted to ground, no zero sequence current high voltage side , its action time users do not need to meet low voltage transformer. Therefore, the action of zero sequence protection phase protection than a short time.
30, on the op amp's basic requirements?
(1) input impedance and external feedback circuit impedance values should be precise and stable; (2) open-loop voltage gain should be large enough; (3) open-loop input resistance ri be large enough (4) open-loop output resistance should be small; (5) zero drift and noise to be small.
31, what is the amplifier output resistance?
the amplifier output, the amplifier can be seen as a signal source with a certain resistance, the resistance is the output resistance.
32, calculated using the superposition principle of linear circuits Which should pay attention to matters?
superposition principle can calculate the voltage and current sources of each under a separate voltage and current of each branch, and then add the principle of superposition, should pay attention to in the application of the principle of superposition (1) the principle can only be used to calculate the linear current and voltage, the nonlinear circuit is not applicable (2) the overlay should pay attention to the direction of current and voltage, replace the number and when superimposed ( 3) circuit connections and the circuit size of the resistance can not change. Role of the current source, voltage source short circuit, voltage source role, the current source open. (4) the superposition principle applies only to the superposition of voltage and current, and power can not be calculated with the superposition principle.
33, why should set the generator over-voltage protection? adjust the turbine control system
slowly, after the load rejection in the accident, promises not to drink prone to over-voltage, so the requirement to set the over-voltage protection.
34, what is the low excitation generator and generator loss of field?
low exciting said excitation current is lower than the static stability limit corresponding to the excitation current. Generator loss of field is the loss of excitation current.
35, why the load voltage generator to be installed over-current protection of their action? Why is this protection to be used at the generator neutral point current transformer?
This is to the next as a generator differential protection or protection of a reserve component of the set, when the failure of the following two works: (1) When an external short circuit, fault protection devices or relay reject action ; (2) within the differential protection of generator differential protection fault refused action.
36, the transformer over-current protection voltage starting compound the negative sequence voltage value in what the general principles of tuning? Why?
system normal operation, the three-phase voltage is basically a positive sequence components, negative sequence component is very small, so the negative sequence voltage components during normal operation by setting the value of the negative sequence voltage imbalance filtered output voltage setting, generally to 6 ~ 12V (secondary voltage)
37, why some high-capacity transformers and system contact with the negative sequence current transformer and low voltage single-phase Overcurrent protection as backup protection.
as such protection has the following advantages: (1) in the event of asymmetrical short-circuit, the sensitivity is high; (2) in the asymmetric short circuit after the transformer, the sensitivity has nothing to do with the transformer wiring.
38, relay any role in the protection of its?
(1) protection of the measuring element of the contact is generally small, the numbers are small, through the intermediate relay capacity and increase the number of contacts; (2) When the line is equipped with a tube arrester, the use of the middle following the electrical protective devices available to delay, prevent arrester discharge of liquid caused by malfunction protection; (3) Protection of logic circuits to meet the needs.
39, electromagnetic relays and voltage relays the current working conditions What is the difference?
voltage relay general access to the voltage transformer secondary side, compared with the current transformer, the voltage is high, so the coil turns the relay
more fine wires, impedance large, and the reactance of the coil increases , as well as current decreases; the other hand the magnetic circuit resistance decreases, while the current decreases and the decrease of mutual impedance compensation during the relay in the action of electromagnetic torque constant, losing relay characteristics.
40, Why is the protection of protected areas from the basic system is running without party change?
because the distance protection is to use the beginning of the line voltage and current ratio as a criterion constitutes protection, short circuit impedance of the line is only the beginning with the short end of the pitch distance changes, so the protection of the protected area system, the basic operation mode changes from effects.
41, starting from the protected device What is the role /
(1) short-circuit fault, the rapid start-protection devices; (2) The starting oscillation locking device, or a double as the first paragraph of the measuring element III; (3) to Do not switch section; (4) Do not switch the phase; (5) protection transistor, if the DC part of the logic fails, the latch complete protection.
42, starting from the protected use of negative sequence components and zero sequence components in place a little increment?
(1) high sensitivity; (2) shows that oscillations do start blocking device components; (3) in the second voltage second circuit break will not malfunction; (4) symmetric components do not appear in the phase failure has nothing to do, so the starting components can be a single relay, so simple.
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