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When transformers are switched on, inrush currents can occur that exceed a multiple of the transformer rated current. Since the inrush current decay again after a few milliseconds, protection devices must separate these from fault currents and block tripping accordingly to ensure correct operation.

If the inrush current is analyzed with a suitable measuring device such as the SHERLOG fault recorder, an increased 2nd harmonic component can be detected. This increased proportion is also used by the protection devices to provide inrush stabilization. If the proportion of the 2nd harmonics exceeds a specified percentage, the trip is blocked by the protection device. 

Since this is a blocking of protection functions, the inrush stabilization testing has to be part of the protection testing. For this purpose, test quantities that are within the tripping range of the protection device have to be superimposed with corresponding proportions of harmonics and the reaction of the relay has to be evaluated. With the VD-Monitor of the ARTES 5 testing software, such test sequences can be created in a simple manner. The ratio between the fundamental signal and the superimposition can be kept constant or changed in steps by means of ramp definition. Thus, combining several test sequences with different settings enables phase-selective testing of the inrush stabilization in a single test routine.

 

Any questions or additions to the topic? Then please use the comment function here in the blog or send an email to bfleuth(at)kocos.com.

Voltage transformer VT2 – Extension for ARTES test systems

Testing of protection devices with rated voltages up to 690 VLL

With the steady increase in decentralized power generation, the requirements for power distribution are also becoming more complex. Due to the increasing plant power, these are often connected directly to the medium-voltage distribution grid, but the individual generation units of a plant are interconnected at the low-voltage level. This is raised to medium-voltage at the grid connection point by means of a transformer.

The low-voltage used within a generation plant results in a high current load on the cables for long distances between the individual generation units. In order to minimize the associated power losses, the nominal voltage on the low-voltage side is increasingly being raised to up to 690 VLL, in deviation from the widely used 400 VLL.

With an appropriate configuration, many protection systems can also measure this increased voltage directly without additional voltage transformers. This automatically results in new requirement for the test systems. These are largely designed for testing voltage protection functions up to a nominal voltage of 400 VLL. In order that these systems can also be used for testing with higher voltages, an extension is offered with the VT2 to also meet the new requirements.

During the development of the VT2, care was taken to incorporate the advantages of the ARTES RC3 relay test system. Therefore, the VT2 was also fully integrated into a hard shell case and is thus also ideally suited for use under harsh conditions.

Do you have any questions about the voltage transformer VT2? Then contact us by mail to info(at)kocos.com

In addition to the hardware of a test system, the testing software also plays a major role in protection relay testing. Even though simple test tasks can be performed with ARTES test systems without a PC using the integrated operator interface, it is only the combination of hardware and software that provides the full range of functions. The testing software is designed to simplify and automate even complex protection tests.

KoCoS meets these requirements with its ARTES 5 testing software. ARTES 5 enables today’s protection engineers to perform their daily tasks quickly and easily. To this end, ARTES 5 offers a wide variety of features that make testing as efficient as possible. 

Database

ARTES 5 is a database-based testing software. This allows centralized management of all necessary settings as well as results and eliminates the need for manual data management. In addition to a simple folder structure, entire plants including voltage levels and bays can be visualized in the topology. 

For data exchange with colleagues or customers, individual data sets or entire structures can be exported from the database to a file. In turn, the information contained can be viewed and edited without importing it into the user’s own database. 

All in One

With the increasing complexity of protection functions, the testing software must provide the user with more and more new tools. In ARTES 5, these tools are known as monitors, and various monitors adapted to different protection functions are provided. All available monitors are included in the standard scope of delivery and do not have to purchased additionally by the user. Regular updates, some of which include new monitors, are also provided free of charge. 

Of course, the ARTES 5 testing software offers much more. For a detailed presentation of ARTES 5 our specialists are at your disposal. Contact us via the comment function or by mail to info(at)kocos.com

The comparison of actual test systems shows that the technical data of the devices from different manufacturers are similar in many points. And there are specifications where the devices differ to a greater or lesser extent. When evaluating, however, it should always be questioned what this means for the practical use of the devices.
 

Specifications as a result of development

In some cases, the technical data are much higher than required by the application. And this was not always the aim during development. Rather, some values are just the result of the development, quasi what has come out.
 

USPs without added value

And there are certainly manufacturers who deliberately work towards generating "unique selling points", which in the end, nobody needs. A real USP only becomes more important when the existing advantages also offer added value and a special benefit for the customer.
 

Technical data does not tell the whole story

Technical data are easy to compare. But purely numerical values say not much about which product is best suited for the customer. Product features and properties that cannot be evaluated with numbers, or only with difficulty, often lose their importance in the comparison. And it is often here where the advantages can be found that offer real added value for the customer.
 

Real USPs are not easy to find

The special features of our ARTES testing systems are pointed out in brochures, articles or blog posts. Customers appreciate, for example, that ARTES can be operated in an upright position. The status LEDs in the front or the operation of our devices on DC supplies are also appreciated by many users.

These properties and the many features and functions of ARTES are often not known. For example, the internal control unit, the low-level outputs, the analogue inputs, the multifunctional inputs or the internal GPS synchronisation unit are already included in the standard scope of delivery of the ARTES 600. In competing products, these features are often found, if at all, as options for which a charge must be paid. ARTES also scores points, for example, with its very low noise level, a feature that is difficult to express in numbers.
 

The software matters

The software plays a major role in relay testing. The device hardware of a test instrument is primarily a freely programmable function generator. Even though ARTES offers much more with its on-site operation, the test software in the end makes a decisive contribution to the high functionality of a professional testing system.

The ARTES 5 software is not only convincing because of its many useful features. It also has the most advanced user interface and the most intuitive operating concept. With ARTES 5, the user reaches his goal faster and easier, and thus saves time. In a following blog post, we will focus on the features and advantages of the ARTES 5 testing software.
 

ARTES experience live

The special features of ARTES are also highlighted regularly in social media such as Facebook, LikedIn, Twitter or YouTube. However, a live demonstration also offers the opportunity to find out what a customer's requirements and needs are. Only then is it possible to work out the features of ARTES that are important for the customer and to demonstrate their benefits.

Particularly in view of the diverse functions of the software, we are always pleased to offer our customers practical product presentations. Here, the customer not only learns a lot about ARTES, he can also experience ARTES live.