SU1117775A1 - Method of selecting fuel-fired steam plant with drum boilers in case of emergency degreasing of frequency - Google Patents

Abstract

A METHOD FOR ISOLATING THERMAL ELECTRIC POWER STATIONS WITH DRUM BOILERS FOR EMERGENCY REDUCTION OF FREQUENCY 1, according to which the current frequency value is measured, compare it with the first and second set frequency settings and at the frequency value. less than the first setpoint frequency, the power plant is separated from the power system with the first time delay set, and when the frequency value is less than the second frequency setpoint, the signal to separate the power plant from the power system with the second predetermined time delay, characterized in that the purpose of improving the reliability of power supply to consumers by eliminating unnecessary separation of a thermal power plant from the power system during emergency frequency reduction, additionally for each electric power unit The stations measure the water level in the boiler drum, compare the measured values with the preset level settings, the separation of the power plant from the power system with the second S time delay is performed at a value of at least one measured level value less than the level setpoint.

Description

At the performance. Oogan divider 1

automatics

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: I The invention relates to electrical engineering, in particular to emergency control automation of power systems. In power systems, it is widely used to isolate thermal power plants with roughly balanced load or individual units with their own needs for a power plant during a deep or prolonged emergency frequency reduction. A deep decrease in frequency, accompanied, as a rule, by a deep decrease in voltage, leads to disruptions in the operation of various mechanisms of the plant’s own needs and, as a result, to the disconnection of the units. A prolonged decrease in frequency leads, first of all, to a drop in the performance of electric power pumps, which results in a further increase in the power deficit in the power system due to a decrease in the power of units with flow boilers and the disconnection of units with drum boilers with technological protection against lowering the water level in the drums of boilers . A known method of separating a thermal power plant with an approximately balanced load (or, individual units with their own load) measures the current frequency value, compares it with a given set point, separates the power plant from the power system with a given time delay, and also monitors directing power flows through various elements of the power system (lines, transformers) or voltage levels on the power plant tires 1. The disadvantage of this method is The possibility of an excessive (premature) release of a power plant at relatively shallow frequency drops, due to the independence of the time delay with which the release takes place, from the levels of emergency frequency drops. The duration of operation of units with drum boilers according to the conditions of operation of technological protection by lowering the level in the drum of the boiler at different levels of frequency reduction is different (the deeper the frequency decreases, the shorter the duration). A time delay (30–40 s) with relatively shallow frequency decreases is selected according to the heaviest mode (possible decrease in frequency to values of the order of 46-46.5 Hz). At the same time, if the frequency is reduced only to levels of the order of 47-48 Hz, the duration of operation of the power units is significantly longer. However, by reducing the frequency to such levels, the separation of a power plant according to this method is carried out earlier (after 30-40 s) than is permissible under the conditions of reliable operation of the power plant. Due to the separation of the power plant (even with an approximately balanced load), the relative shortage of power in the separated power system increases, the conditions for the occurrence of an accident in it become worse, and the volume of the load disconnected from the AChR increases. The closest technical solution to the invention is a method of separating a thermal power plant, including with drum boilers, according to which the current frequency value is measured, compare it with the first (usually 45-46 Hz) and the second (usually 47-48 Hz) by the specified settings, and with a deep decrease in the frequency (below the first setpoint) the power station is separated from the power system with the first predetermined (low) exposure time (usually 0.5-1 s), and for a long time, relatively shallow reduction frequencies (below the second At the given setpoint, the power station is separated with a second (relatively large) predetermined time delay (typically 30-40 seconds). 2. The disadvantage of this method is a decrease in the reliability of power supply to consumers by improving the separation of power stations at shallow frequency drops. The purpose of the invention is to increase the reliability of power supply to consumers by eliminating unnecessary sections of a thermal power plant from the power system during an emergency decrease in frequency. The goal is achieved by the fact that, according to the allocation of a power plant, the current frequency value is measured, compared with the first and second given frequency settings and when the frequency value is less than the first; of the setpoint frequency, the power station is separated from the power system with the first time delay set, and when the frequency value is less than the second frequency setpoint, a signal is generated to separate the power station from the power system with the second time delay set, the water level is also measured for each power plant unit the boiler drum, compare the measured values with the specified level settings, the power plant is separated from the power system with a second time delay at a value of at least one th layer measured quantities less than the level setpoint. According to the proposed method, the separation of a power plant in the event of a long but shallow frequency reduction occurs only with a simultaneous deep decrease in the water level in the boiler drum of at least one station unit. By reducing the frequency, not leading to a deep decrease in the levels in the boiler drums, the electrical growth is not released, as a result of which

The relative power shortage in the separated power system does not increase, i.e., the reliability of power supply to consumers increases.

The drawing shows a block diagram of the device for drying the proposed method.

The device comprises a first frequency measurement body 1, a first time-delay body 2, a second frequency measurement body 3, a second time-action body 4, bodies 5 for measuring the water levels in the boiler drum, a logical element OR 6, and a logical element AND 7.

The frequency measurement organs 1 and 3, the inputs of which are intended to be connected to a voltage transformer, serve to measure current, its frequency value and its comparison with the given settings of these organs, respectively, fjycr and fzvcr. When the frequency drops below the set points of organs 1 and 3, signals appear at their outputs; at a frequency higher than the settings of these organs, there are no signals at their outputs. For example, frequency down relays can be used as frequency measurement units. Organs 2 and 4 of the time delay are intended for counting predetermined time delays, tivcr and tgycT, respectively, when signals from organs 1 and 3 of the frequency measurement are fed to the inputs of these organs. If there is an input signal from the frequency measurement organ at the input of the organ after a predetermined time delay at the output of the time organ, a signal appears. When the time delay signal is removed at the input of the time delayed organ until the end of the countdown of the specified time setting, this timeout stops and when the signal appears again at the time delay body input, the time delay reading begins. In the quality-time delay bodies, for example, time relays can be used. The setting for frequency fjyci of organ 1 is low (usually 45-46 Hz), the setting for frequency fzycr organ 3 is relatively high (usually 47-48 Hz). The time delay tiytr of organ 2 is taken short (usually 0.5-1 s), and the time delay tjyiT of organ 4 is relatively long (usually 30-40 seconds).

The water measuring organs 5 in the boiler drum are designed to measure the current value of h levels and compare them with the predetermined set points h mouth. The number of organs measuring the levels is equal to the number of boilers. When the level in the boiler drum drops below the setpoint h, a signal appears at the output of the corresponding level measuring unit, and at levels higher than h mouth, there is no signal at the outputs of the organs 5. As organs for measuring levels in the drums of boilers there may be.

for example, level sensors are used. The setpoints of the hycT level measurement bodies are taken slightly higher than the setpoint of the anti-drop protection in the drums of the boilers acting on the shutdown of the units.

Logic element OR b is designed to form a signal when any of the n organs are triggered, the level in the boiler drum is measured. The signal at the output of the element OR b appears when the signal is applied to any of the n inputs. In the absence of signals at all its inputs, the output signal of element b is zero.

The logical element And 7 is designed to generate an output signal supplied to the executive body of the dividing automation, only if there are simultaneously signals on. its inputs from the body 4 time delay and the element OR b. In the absence of both or one of these

0 input signals the output signal of the element And 7 is missing.

The device works as follows. In normal mode (at a frequency higher than the settings of organs 1 and 3 and the levels in the boiler drums are higher than the settings of organs 5) there are no output signals from organs 1, 3 and 5 and, as a result, organs 2 and 4, elements b and 7. As a result the signal to the executive body of the dividing automatics is not received.

When the frequency decreases below the setpoint of organ 1 (deep decrease in frequency), a signal arrives at its output, which is fed into organ 2. After the time delay of this organ expires, a signal arrives at the executive organ of the separating automatics. When the frequency decreases below the setpoint of organ 3 (a relatively shallow decrease in frequency), a signal is delivered to its body 4. After the time limit of the organ 4 has expired, a signal appears at the output of the first EIT of the element 7. At the absence of a signal at the second input element And 7 its output signal is zero, and the automation does not work. When the levels in the drums of the boilers 5 fall, when the frequency decreases and the setpoint reaches one of the drums. An empty organ 5 of the level measurement sends a signal to the corresponding input of the OR element, resulting in a signal to the output of this element, which is fed to the second input element And 7. If there is a signal at the first input of element And 7, a signal appears at its output, which is fed to the executive body of the dividing automation. Thus, the separation 5 of the power plant is provided only with a simultaneous long-term reduction in the frequency (operation of organs 3 and 4) and a decrease in the level below the setpoint at least at 117775 56

Nom of the boiler drums (when triggered there are no, the dividing automatics are not unequal to n organs 5). When running for a long time, the power station does not separate the frequency reduction, which does not lead to deep energy systems, as a result of which the signals at the outputs of elements 6 and 7 increase the reliability of the power supply to consumers by reducing the levels in the boiler drums.

Claims (1)

METHOD FOR SELECTING A HEAT POWER PLANT WITH DRUM BOILERS DURING EMERGENCY REDUCING FREQUENCY, according to which the current frequency value is measured, it is compared with the first and second preset frequency settings and when the frequency value is less than the first preset frequency setting, the power station is separated from the power system from the first time and when the frequency value is less than the second predetermined frequency setting, a signal is generated to separate the power station from the power system with a second predetermined time delay, distinguishing In order to increase the reliability of consumers' power supply by eliminating unnecessary separations of the thermal power station from the power system during an emergency reduction in frequency, in addition, for each power plant unit, the water level in the boiler drum is measured, the measured values are compared with the set level settings, the separation of the power station from the power system with the second time delay is produced when the value of at least one measured level value is less than the level setting. SLL "" 1117775 I