Loss of Mains Protection
(LoM Protection) Devices
LoM protection systems are of vital importance for renewable energy installations, such as PV installations and industrial generation facilities. There are two basic types of LoM protection system—internal protection and external protection—and the feed-in capacity of the system determines whether internal and/or external LoM protection is required. Internal LoM protection is generally used for inverters with low feed-in capacity. For larger installations, external LoM protection in the form of a LoM protection relay is usually required. In both cases, the anti-islanding protection is an important feature. In the event of a fault, it isolates the installations or smaller island-capable sub-networks from the distribution network by means of a circuit breaker. Apart from immediately isolating the installation in the event of a fault, another function of the system protection device is to support the network the moment the power system fault occurs (fault ride through).
Both types of system protection are indispensable in terms of ensuring fault-free operation of the distribution network and a high security of supply of electrical energy. Testing is a crucial aspect during both commissioning and routine maintenance. An increasing number of smaller companies today are also offering protection testing as a service.
Those using test sets during commissioning and maintenance activities should have the best possible support, so their devices should be able to accommodate ad-hoc tests for quick, easy, and efficient testing. This is particularly important, as testers have to visit a wide variety of locations and tackle constantly changing testing conditions and very different protection functions.
In principle, the LoM protection functions are relatively simple. However, the requirements for the testing are determined by the specifications of the network operator (feed-in regulations, connection requirements, grid code, etc.) to whose power system the relevant generation facilities are connected. And this is where the specifications for the anti-islanding protection differ depending on the country and standard.
Standards and Guidelines
Specific regulations, guidelines, and standards defining the minimum LoM requirements apply when connecting a generation facility to the public low-voltage grid. At an international level, these are the standards laid down by the International Electrotechnical Commission (IEC). EU guidelines also form a basis within Europe. These are supplemented in the individual countries, such as Germany, by the additional requirements set out in the VDE and VDI guidelines. In addition to the network protection tests carried out during commissioning, routine maintenance tests are also stipulated. In Germany, and in some other countries, protection testing certification is already mandatory. These legally enforceable measures ensure that installations are protected with a high degree of reliability, as well as defining what actions have to be taken in the event of a power system fault or voltage dip.
Examples of such standards and guidelines are:
- VDE-AR-N 4105 and VDE-AR-N 4110 for Germany
- Technical and organizational rules for the operators and users of networks (TOR-Generator)
- ENA EREC G99 (successor to G59) for the United Kingdom
- IEEE 1547 for the USA
Testing LoM Protection Functions
Protection relays are the central component of LoM protection systems. Numerous tests to ensure correct operation are carried out over the life span of a relay. Typical examples include protection relay testing during commissioning and function testing during routine maintenance activities. However, testing is not an easy job, as the quantity and variety of the equipment to be tested is increasing all the time. In addition, the various requirements set out in the standards, guidelines, and regulations must also be observed during protection testing.
We support you with appropriate solutions for the testing of protection relays as part of an overall network and system protection concept. These solutions cover:
- Anti-islanding protection (U>, U<, f>, f<, ROCOF, etc.)
- Reactive power directional protection, undervoltage protection (Q-V protection)
- Automatic under-frequency load shedding (UFLS)
- Short-circuit protection functions of various equipment manufacturers
These tests can be carried out either manually or automatically.
Manual testing
In the case of manual testing, the test steps for the individual protection functions of each installation are specified in a simple and intuitive way. All input is made manually using the touchscreen and control wheel. The CMControl unit offers unparalleled flexibility during use, whether fitted to the test set, operated as a hand-held unit, or attached to steel surfaces via magnetic force. You can even operate it using a laptop or tablet via the CMControl P app, which reproduces all the functionality of the CMControl unit. The advantage of the CMControl P app lies in its intuitive user interface, which guides the tester step-by-step through each test.
Manual testing of a QV relay with higher-level anti-islanding protection can be a little more complicated, so we've provided a Getting Started guide as a PDF.
Manual testing of a QV relay442 kB (PDF)
Automated testing
Automated testing lets you save test procedures and access them again for use on other installations. Our Protection Testing Library (PTL) contains a number of ready-made test templates to keep the effort involved in testing to a minimum. These tools allow you to create customized test procedures that you can easily reproduce, which significantly reduces the time involved in running tests.
Automatic testing—protection applications
Our Solutions for Commissioning and
Testing LoM Protection Systems
CMC 310
The CMC 310 is a lightweight (13.1 kg, 28.9 lbs) and compact protection relay test set for rapid, manual, single- and three-phase testing. It comes especially recommended for medium-voltage distribution networks, industrial applications, process control, as well as for lower-level and higher-level network and system protection devices. The modular CMControl unit is used to operate the CMC 310. The CMC 310 test set can be upgraded to a CMC 353 whenever required, offering you an even wider range of applications options.
The CMCheck RE test software, which runs on the CMC 310, is the perfect choice when testing anti-islanding protection in photovoltaic installations. It simplifies testing and gives you reliable support when preparing the test reports required for the official certification process.
CMC 500
Mastering all the challenges of protection relay testing with just one test set and thus making an essential contribution to the energy system's reliability? Now you can with the lightweight and compact CMC 500! Thanks to our modular hardware and software concept, the CMC 500 fulfills your requirements perfectly while meeting the highest safety standards.
CMC 430
Weighing just 8.7 kg (19.1 lbs), the CMC 430 is extremely portable and supports the output of three currents of up to 12.5 A each and six voltages up to 150 V. The application range can be expanded to 600 V (L-N) when used in combination with the VBO3. Like the CMC 353, it creates scope for generic test procedures that allow identical tests on network and system protection devices to be carried out using an automated test procedure. You can also access these on our Protection Testing Library (PTL) for automated testing. The PTL includes templates for testing anti-islanding protection equipment according to VDE-AR-N 4105, VDE-AR-N 4110, the TOR-Generator, and G99 standards.
Protection Testing Library (PTL)
Automated test templates from the Protection Testing Library can be used with protection relay test sets like the CMC 353 or CMC 430 that are compatible with Test Universe. The test templates also include templates for testing anti-islanding protection according to VDE-AR-N 4105, VDE-AR-N 4110, and the TOR-Generator standards. These let you create customized and easily reproducible test procedures, thus significantly reducing testing times.
VBO3
Higher voltages of, for example, 400 V (L-N) [690 V L-L] can also occur during tests on industrial networks and installations that generate renewable energy. The VBO3 is a three-phase voltage transformer with a transformation ratio of 1:2. It expands the application range of a CMC to up to 600 V (L-N).
CMTAC 1
In many cases, renewable energy installations, such as wind farms or PV systems, do not have a battery system that can supply auxiliary DC. These installations therefore often use 230 V AC for their control signals. The CMTAC 1 enables both the CMC 310 and the CMC 353 to also measure trigger signals in the AC voltage.
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Need any help?
Our technical support team is on hand to assist you. Our English-speaking engineers are available 24/7; German-speaking engineers are available from 8 am to 6 pm, including weekends. Regardless of whether you have a question about how to operate a test set, how to carry out measurements, or about the software or technical systems, our highly qualified engineers will be there to help you. You can count on us. In addition to an in-depth knowledge of our products, our dedicated support team also has a detailed understanding of every application in the field of network and system protection. We know the work you do is incredibly important in terms of keeping our power grids operating reliably, so we are pleased to offer you a comprehensive support package from installation, through to training and troubleshooting. We help you ensure your tests are efficient, accurate, and reliable—so you can keep your network and system protection devices operating smoothly.
Click here to contact our technical support team.