Synchroscope

The synchroscope is an electrical engineering instrument which serves in transformer substations and power plants to ensure the interconnection of synchronous AC power sources such as generators or the merger between electricity grids.

Are compared with each other while the three parameters, the amplitude of the voltage, the phase position of the mains frequency and the different network areas. The successful switching operation takes place at the synchronization point, that point at which the three sizes are within the permitted variations against each other. Become an asynchronous AC voltage sources or AC systems not connected together at the synchronization point, or are the three parameters outside of their tolerances, it can (eg protective devices ) lead to stress cracks and misconduct of other electrical devices in the network. In the worst case, the asynchronous interconnecting the faulty interconnecting an electrical short circuit is the same.

Construction

The synchroniser ( Synchronisiersäule ) in this case contains all instruments necessary for synchronization and consists of

• Double voltmeter
• Double frequency meter
• Shift indicator synchroscope

In operation service to synchronize manually, semi-automatic synchronization and almost exclusively used in large interconnected systems fully automatic synchronization are still common in smaller installations in special cases. The fully automatic synchronization provides the advantage that switching errors can be excluded with high probability.

Synchronization

The synchronization is performed manually by connecting the respective branches or power supplies by turning on the associated circuit breaker, in compliance of the inherent runtime, the synchronization point. In this case, a so-called Synchronisiersteckschlüssel is used, with the power switch of the waste stream is switched in consideration of the synchronization conditions.

Electrical Equipment mainly be carried out by the Einschlüsselmethode, with a Synchronisiersteckschlüssel for the whole plant is employed. In the two key methods of synchronizing breaker is operated in the parallelzuschaltenden leaving and that used for parallel connection finish.

The semi-automatic synchronization by parallel connection of the respective branches and power supply by turning on the associated circuit breaker at the synchronization point with parallel switching device. The paralleling unit issued after selecting the appropriate branch or outgoing circuit the switching pulse for the circuit breaker taking into account the shift schedule time and the switching slip. Voltage and frequency in the network are not affected by the device. The shift setting time is the time that must be given to the switch-on of the power switch under consideration of the inherent time as well as the control and relay times to allow parallel connection at the synchronization point. When switching slip is defined as the maximum permissible frequency difference, which is dependent on the network and the constants to be synchronized performance or interpretation of the generator in order to avoid larger transient currents with oscillations when switched in parallel.

The fully automatic synchronization by parallel connection of network components by turning on the associated circuit breaker at the synchronization point with parallel switching device that operates in conjunction with a voltage and frequency adjustment device. The control system allows that today synchronizers have more functions on the basis of often different system configurations. In order to cover all the necessary system configurations, feature modern Synchronizing several Synchronisierarten. These can be, for example:

• Generator with net or line
• Synchronous or asynchronous networks or lines
• Check for synchronous switching händisches
• Busbar quick switch
• Measurement of the circuit breaker operating time

Preparation of the compound with the network

The synchronous machine is to be mechanical (eg turbine ) coupled with a work machine. The connection of the anchor lines to the rigid network is not yet established. The circuit breaker as a link is opened. The machine drives the synchronous machine with an arbitrary rotation speed n. The exciter winding of the synchronous machine is fed with direct current. Since the armature carries no current, a magnetic field is built up in this idle with open armature terminals only from pole system here, which is then equal to the resulting field.

The armature winding of the synchronous machine is running in a star configuration. The strand to be considered authoritative for the voltage induction in the magnetic flux here is the angular frequency and the induced voltage of the same frequency. This is observed as a clamping voltage

A voltage whose magnitude is proportional because of the speed, and because the excitation current and whose frequency is given by the current speed of the synchronous machine. Your instantaneous value can be represented as follows as

The voltage of the network, which the synchronous machine is to be connected, has the magnitude and the angular frequency. This voltage can be presented for consideration to the strand as follows

Of the breakers for connection to the fixed network can be switched without a current begins to flow, if before switching the voltage in each moment

Is. This follow as the synchronization conditions that must match the voltages of the synchronous machine and the network corresponding to the three pieces of a sinusoidal signal determination by RMS, frequency and phase angle. So it must be true:

The easiest way to monitor compliance with the synchronous conditions, the so-called Synchronisiersäule. The two voltmeter (voltage synchronous machine or voltage of the network) are combined in a double voltage meter, wherein the pointer of the two measurement units of a scale are assigned. Likewise, the two rate monitors are designed as a double -frequency knife in which the rows of oscillating tabs are juxtaposed in a housing. To monitor the phase angle or phase displacement of the voltages and phase are known lamps.

Circuit variations

A distinction is made in the circuit of phase lamps between dark and light circuit circuit.

In the dark-on the interlock conditions are fulfilled, if the two voltages ( the synchronous machine and the network) have been made ​​to coincide with regard to their frequencies and amounts then also have the same phase, when there is no voltage across the switch contacts, such that the parallel-connected lamps not light up.

In the light-on mode, the synchronization conditions are met if also brought the two voltages in terms of frequency and amount in accordance with and in the same phase is reached. Here, the phase lamps are not connected in parallel to the circuit breaker contacts, but between the conductors. The stage lights then light up in sync point on light.

The phase voltages for the lamps are provided via the power converter of the two systems. The stage lights are currently used only in test mode. Instead of lamps occurs the synchroscope. This is a device in which a pointer, the deviation of speed of the engine from the required synchronous speed and because of its location to a fixed mark indicative of the direction and speed of movement, the phase shift between the two voltages. Its effect is based on the comparison of two rotating fields, one of which is from her network and the other is built on the synchronous machine manufactures. By adjusting the speed of the prime mover organ the pointer moves faster or slower. Parallel switching occurs when the pointer reaches the clockwise rotation in slow running the brand of the synchronization point. To perform a proper synchronization by hand, the synchronizer is provided with a parallel shift lock. This prevents the power-on, when the voltage difference is too large or the speed of the engine is not true.

The measures are required to meet the interlock conditions are referred to as synchronization. The rotating field equality of networks is realized before the first commissioning of the plants. Then one starts to bring the frequencies of the two voltages in accordance. These must be changed according to the speed of the synchronous machine. This is done by engaging the speed control organ of the prime mover. Subsequently, the values ​​of the two voltages are adjusted by changing the excitation current of the synchronous machine. This order is required because the machine voltage in the other case, when you first amount would be adjusted by changing the excitation current to the mains voltage, would alter the subsequent frequency tuning by changing the speed also.

After the two voltages on the frequency and amount match, they may differ only by the phase angle. This phase shift is eliminated by again, a brief intervention is carried out in the speed control organs of the prime mover. Characterized the frequency of the machine voltage is changed during this time. These short-term frequency change must be completed in phase coincidence if there is no voltage across the circuit breaker contacts. If the synchronization conditions are met, the power switch can be turned on without begin to flow compensating current. In this case one speaks of a fine synchronization. The machine is with electroless anchor on the network. By re- engaging the speed control organ of the prime mover as an active energy turnover is now enforced.