OMICRON electronics

Modern Test Equipment: Economic Value through Safety

The design changes to relay test equipment over the past ten years is nothing short of incredible. From basically an integrated load box and variac, the modern relay test set has evolved into an integrated system of computer-controlled specialized pieces, that allow amazing flexibility in defining the tests required for today’s relays. These test sets can now be considered portable three-phase simulators, but the price of modern technology is not cheap. These test sets are on average 3 to 4 times the cost of their single-phase relatives, so what justifies their cost?

Often the full value of these modern test sets remains unrealized by the purchaser, who is often only concerned about the "hard dollar" savings this equipment provides. But with any new purchase, the "soft dollar" savings should also be considered. Such is the case with modern test equipment where numerous factors account for these soft savings. Often the "safety" considerations are overlooked. So what "safety" features "add value" to your purchase and provide enhanced economic payback?

1. Protect your workforce: New designs utilize the latest in safety plugs, connectors and connections making for fewer hazards and accidental electrical contact with the test equipment during operation. New test equipment designs are typically computer-controlled or actually have a computer built-in. This allows for internal diagnostics, which can alert when dangerous situations occur, like an ungrounded power source or high impedance ground connection, which could pose a hazard. Other diagnostics will only allow the equipment to operate when all of its internal systems are properly operational.

Design of a modern test set utilizing new amplifier technology is much lighter and delivers more flexibility than older transformer-coupled amplifier designs. This means less weight, easier to lift and move, and fewer personnel injuries. (i.e. fewer workman’s comp claims). This makes meeting local safety standards (like OSHA) easier, and expands the workforce possibilities by removing exclusions due to equipment weight.

2. Protect your investment: New amplifier designs are self-protecting. This means even if the test equipment outputs are accidentally shorted or open-circuited, they simply shut off and prevent any damage. And they also protect themselves internally with over-temperature sensors when driven to the limits of their power capacity and reach their thermal limits.

So how can you be assured that you will get these benefits from the test equipment you purchase? Carefully compare features and make sure you know your local safety requirements. Many local requirements reference international standards for safety compliance. These international entities are UL (USA), CE (Europe), CSA (Canada) and TUV (Germany) to name a few. Many safety standards are duplicated by these entities, therefore reciprocity is directly recognized between most of them and only one reference is required.

With the OMICRON CMC Test Equipment you can be sure. The following is a table of recognized standards, with cross-reference, that apply to this class of modern test equipment and are met by the CMC test system.

Challenged by Harmonics?

Introducing our New Harmonics Generator Tool

OMICRON’s new Harmonic Generator Utility for Windows assists you in the creation of harmonics test files when a critical investigation becomes necessary. Up to 3 voltages and currents with superimposed harmonics can be defined. Using these harmonics files with OMICRON’s TransPlay Utility or Advanced TransPlay Test Module provides the powerful tool you need when critical questions arise like:

• What happens to the Relay when harmonics are present?
• Is the Power Quality Meter calculating THD correctly? And, will it trigger a recording at the desired harmonics level?
• What cos Phi does the Energy Meter calculate when power system produces harmonics?
• Does the Synchronizing device fail because of harmonics?
• Generate up to 6 signals (3 x voltage, 3 x current) with the same fundamental frequency but individual amplitudes, phase shifts and harmonic content.
• Harmonics up to the 30th harmonic can be generated. (25th harmonic @ 50Hz, 20th harmonic @ 60Hz.)
• Duration of 10000 periods can be generated.
• COMTRADE output format for versatility.

A Universal Test Template for any Distance Relay! … Hard to Believe, but it is True

The power of this feature is based on the fact that it is possible to design a Universal Test Template, which has the flexibility to test any relay from any manufacturer including impedance characteristic and reach zones. In the next figures a Universal Test Template was developed based in a SEL 321 relay with Mho characteristic (load encroachment). When this test was complete, the same template was used to test a SIEMENS relay 7SA511 with quadrilateral characteristic. As soon as the template is complete, it is easy to add extra testing points, if necessary to test the other relay. This feature is part of the Advanced Distance Module, included as part of our Advanced Protection Package.

With OMICRON software, a test plan can be developed in a few minutes, (OMICRON’s OHM law for testing) in 3 simple steps:

1. Object parameters where the general parameters and settings of the relay are defined. There is a database with samples of a large number of the relays in the market, sorted by manufacturer.

2. Hardware configuration, where the connections of the amplifiers and the relays are defined.

3. Module to be used according to the type of relay to be tested. The testing points and testing lines could be added manually or automatically for a customized test plan.

Just as today's multifunction relays allow standard protection functions to be combined in various ways to create a customized complete protection system in the one box. OMICRON allows tests to be combined in the same way to create a customized one button test for the complete system. The best test plan for a more reliable test should be based on:

• Manufacturer recommendations
• Protection specialist criteria
• Special conditions of the power grid
  where the relay is working (e. g.
  power swing, method of grounding).

Something to Think About for Just a Minute:

Test procedures recommended by the manufacturers (especially for old relays) are based on the test equipment technology available when the relays were designed. With these technologies, it was impossible to simulate some of the actual situations that the relay had to deal with during real conditions, and the tests were very limited (the job of protection in the power system is not an easy one!!!). The best example is differential protection where for decades this has been tested by simulating a one-phase short circuit on a phase by phase basis (recommended by the relay manufacturer). But how does the protection behave under a 2 or 3 phase short circuit? Well, sometimes when we leave the substation, we assume the risk of a non 100% test, and just cross our fingers, hoping that the relay is going to do a good job under conditions we couldn’t test.

The algorithm of the modern relays takes into account more and more the real conditions (e. g. pre-fault state, harmonics, etc.) of the power system during a fault or disturbance in order to better discriminate (and trip or not trip) the protected element. Everybody knows that the best test set for a protection is a real fault, but have we considered how closely our test system matches the reality? Are we simulating only 50 or 60 hertz faults?
What about DC component, harmonics, pre-fault conditions, …..etc.

Are we testing all the new built-in control functions associated with the protection (load encroachment, switch onto fault, echo logic, etc.). Digital relays have brought more testing challenges and responsibilities for
the protection specialist. Better tools are needed to overcome these challenges, and the ones expected with the relays now being developed for the future? How are we confronting the present and the future?

So why continue to do the same test over and over when OMICRON provides the leading equipment for a more reliable test, based on more realistic conditions of the power system!!!

OMICRON test sets are not simple units for the basic testing of the relays but can do a lot more. Now users can test all protection functions (digital or electromechanical relays) and control logic associated with the protection, energy meters, transducers and synchronizing devices. Also, they can calibrate any equipment which needs an accurate, steady and clean signal of voltage, current, frequency, phase and test. With OMICRON, testing specialist can feel more confident knowing they did a quality job.

REMEMBER!!!