Therefore, they shall contribute to voltage level maintenance in low-voltage grids during normal mains operation. For this reason, application guide VDE AR-N "Generators connected to the low-voltage distribution network - Technical requirements for the connection to and parallel operation with low-voltage distribution networks" has been prepared by FNN and incorporated into the VDE body of standards in August Application rule VDE-AR-N summarizes the main points which shall be considered for termination on the low-voltage grid so the security and reliability of the mains operation are maintained in accordance with the provisions of the energy industry law also with an increasing proportion of decentralized generators and the limit values of voltage quality formulated in DIN EN can be met. The same applies to type testing.
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ICS Prestandard Selbstt? Jede Art der Vervielf? K VDE-Vertr. Der Zusammenhang der zitierten Normen mit den entsprechenden Deutschen Normen ergibt sich, soweit ein Zusammenhang besteht, grunds? It prevents the unintentional supply of electrical energy from the generator into a subnetwork disconnected from the rest of the distribution grid islanding , thereby offering additional protection to the measures specified in DIN VDE VDE , 6. In the case of faults in the low voltage grid, the automatic disconnection device protects the generation plant from — — inadmissible voltages and inadmissible frequencies.
The automatic disconnection device does not protect the generator from overload and short circuiting. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document including any amendments applies. Note: The automatic disconnection device, which may be integrated in the generator, can obtain its supply voltage from the grid. Connection to the grid is also necessary for voltage and frequency measurement.
Passive elements e. EMC filters can also be incorporated unswitched on the grid side. Possible causes for the disconnection include switching actions of the network operator, the triggering of protection devices or failures of equipment. The network has no influence over the voltage and frequency of the disconnected subnetwork. NB: This current may have a capacitive component, caused especially by the use of capacitors. Before feeding into the grid, it is measured for 30 s to check whether the voltage and frequency remain within the tolerance band as defined in 4.
If this is the case, the can be connected and start feeding into the grid. From this time on 4. Following a disconnection of the generator triggered by one of the safety functions of the disconnection device, the connection is carried out in the same manner. Following a disconnection because of a short grid failure, the generator may be connected again once the voltage and frequency of the grid are within the tolerance band specified in 4.
Unintended islanding must also be detected when generation and consumption match each other in the separate network subsection. It may be a stand-alone unit or an integral part of the generator. It must switch off and show the fault status in the event of a failure. An individual fault in the disconnection device should not result in a loss of the safety functions. Faults triggered by the same cause must be considered if the probability of the occurrence of such a fault is significant.
If possible, the individual fault must be displayed and it should trigger a disconnection of the generator. NOTE 1 This requirement for detection of individual faults does not mean that all faults have to be detected. A large number of undetected faults can therefore lead to an unintended output signal and to a dangerous state. NOTE 2 This system response means that — — — the safety function remains operational when an individual fault occurs some, but not all, faults are detected an accumulation of undetected faults can lead to loss of the safety function.
Requirements on the switches 4. At least one switch must be a relay or contactor and be suitable for overvoltage category 2. In the case of single phase feeding units the switch must have a contact of this overvoltage category both for the neutral line and for the phase line. In the case of multiphase feed units, one contact of this overvoltage category is required for all active lines. The second switch may consist of the electronic switching elements of the inverter bridge circuit or another circuit if the electronic breaking elements can be switched off by control signals and it is ensured that a failure is detected and will stop operation at the latest when the feeding in is startet the next time.
It shall not be possible to change this limit in the device. A floating average should be measured over a 10 minute interval for each phase conductor being fed into. Exceeding this set value must trigger a break. The setting of this limit should only be made in consultation with the network operator. For this, either the malfunction itself or a measured d. Alternatively, the automatic disconnection device can receive disconnection commands via an interface from another protection device with equivalent island network detection.
A disconnection command must lead to a disconnection within 0. The protection device issuing the signal and the interface must also fulfil the functional safety requirements defined in 4. In the event of a failure, the d. An external residual current device is required in a disconnection device without an integrated RCMU.
In this case, the tests defined in 6. The residual current device required should be specified by the manufacturer in the operating instructions. Leakage currents greater than mA must trigger a break within 0. Irrespective of the rated power of the inverter, any sudden residual currents should trigger a break as in Table 1. Table 1 - Maximum break times r. In the case of inverters without simple separation between the grid and the PV generator, both switches mentioned in 4.
NB: A design featuring an interrupting device between the inverter and PV generator and an interrupting device between the inverter and grid is possible. A separate disconnecting device should be tested together with a suitable generator. It should be ensured that the break signal is generated by the disconnection device and not by the generator. The trigger time specified in 4. The test shall be carried out for each phase conductor which is fed into.
The trigger time of the frequency monitoring specified in 4. Functioning of the frequency monitoring shall be checked within the voltage range specified in 4. The break should happen within 0. By simulating a fault a measurement should be taken to determine whether defective operation with a direct component of the input current of over 1 A triggers a break within 0.
Testing of the break following direct current feed is conducted using optionally a or b : 6. The method used must fulfil the functional safety requirements set out in 4. Even under these conditions the automatic disconnection device must reliably detect the interruption to the network and switch off the generator within 5 s. The test circuit has the following properties: The direct voltage side of the inverter is supplied by a variable energy source.
In the case of generators with no inverter, the power supply is provided by a suitable drive. Figure 2 - Test circuit as per 6. The rated power should also be set for generators without inverter. Break device S is then opened in this state. A break should be triggered within 5 s of the break device opening. If the voltage and frequency are within the tolerance band, the disconnection device should not reconnect until at least 30 s after the break.
Between 20 s and 60 s after the disconnection device has reconnected, break device S should close and not reopen until at least 30 s later. This test should be repeated at the different network impedances. To test a 3-phase disconnection unit, a test circuit should be connected to one of the phases in each case, as shown in Figure 2. The other two phases are then connected directly to the grid.
The breaks should each be triggered within 5 seconds of the break device S opening. In the case of generators with no inverter the power supply is provided by a suitable drive. Resistors, reactors and capacitors are arranged in parallel to the output on the a. These form an RLC oscillating circuit and can be finely adjusted to the active and reactive output generated Figure 3.
Both the RLC oscillating circuit and the generator should be connected via separate switches to the grid or a suitable grid simulator. This oscillating circuit should have a Q factor of at least 2.
U 2 where U is the grid voltage, f the grid frequency and P the reactive power fed from the generator. Figure 3 - Test circuit as per 6. The output of the generators is determined using the direct voltage source or a suitable drive for systems without inverter. The system is connected to the grid or the grid simulator by closing S3 and S2. Without any oscillation circuit connected S1 opened , the active P and reactive PQ,WR output flowing into the grid is now measured.
The generator is disconnected from the grid S2 open. The oscillating circuit is balanced as follows: 3. NB: The purpose of the comparison is to keep the fundamental components of the current as small as possible using S3.
Fine tuning of the oscillating circuit step 6 allows the worst possible conditions to be created in terms of possible islanding. To start the test, S3 is opened and the time until the device switches off is measured. After each successful test one parameter L or C is altered by approx.
The entire test is deemed successful if the break time for each individual test is less than 5 s. To test a 3-phase disconnection device, a test circuit should be connected consecutively to each of the phases, as shown in Figure 3.
The other two phase lines are then connected directly to the grid. Here, the requirements regarding functional security given in 4. NB: Three-phase voltage monitoring is also permissible where a number of single-phase feeders which feed into different phase conductors are integrated in a single unit if the currents of these feeders are controlled independently of each other so that different phase relations can be set.
In order to test the voltage monitoring, the automatic disconnection device should be run via an alternating voltage source with variable amplitude at nominal alternating voltage and any output. The test should be repeated for all phase line combinations.
NB: These voltage limits ensure that the voltage monitoring does not trigger during the test.
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DIN VDE V 0126-1-1:2013-08;VDE V 0126-1-1:2013-08