The Siemens SIPROTEC Compact range of protection relays already support low power CTs and VTs. Next year SIPROTEC 5 will support them too – via a couple of new I/O expansions modules. So what’s the big deal about low power CTs and VTs? Traditional CTs have been around a long time so their use is ‘standardised’, which means they are relatively low cost and they are reliable. However for protection applications, a lot of careful engineering must go into sizing of the CT. In addition, much of the setting and protection element design is not so much ‘protection related’ but rather catering for the possibility of CT saturation during a large fault and secondly, not truly reflecting the primary current.

So why consider Lower Power CTs (LPCTs)?

• LPCTs do not suffer from saturation – eliminating one of the biggest protection headaches.
• For panel builders, due to the linearity, one LPCT can be stocked compared to having different traditional CTs ratios for different loads – that is: less inventory and more flexibility.
• LPCTs have a better frequency response, so support improved (more truthful) PQ monitoring.
• The smaller size and weight of LPCTs makes for an overall smaller switchgear (yes – increasing the panel width of switchgear just to accommodate the CTs is common – and expensive).
• With LPCTs open circuit secondary connections are not hazardous.

Low Power VTs have similar advantages, but the biggest is the dramatic reduction in size/weight and price.
In fact, Low Power VT monitoring of each incomer/feeder on a switchboard becomes a cost-effective alternative, eliminating the troublesome bus VT (troublesome from a point of view of fusing, testing, isolating/earthing).

For more reading on this subject download this CIRED conference paper.

PAS is a Siemens ‘Power Automation System’, which is a software platform for utility substation use. Here within New Zealand, its main use is to interface from the IEC 61850 communications between substation IEDs to the remote DNP SCADA master. In these cases the PAS becomes a data concentrator, protocol converter and gateway. The PAS supports other substation protocols such as IEC 103, DNP and MODBUS . In addition, the PAS also provides local automation functionality, and optional bolt-on modules for automatic fault record extraction, centralised power quality database reporting, and the ability to provide local/remote HMI displays.

One of the key benefits of PAS is its ease of use, where mapping of points can be achieved with minimal efforts. New licencing options available in ‘PAS Compact’ now allow the PAS software to be cost-effectively deployed in smaller substations, so feel free to contact us to discuss how PAS can work for you.

The recent upgrade of the popular PQ-Box 100/150/200/300 Power Quality Analyser setup and evaluation tool 'WinPQ mobil’ provides: Ability to correct the phase angle of miniature current clamps Simplification of templates - for those fortunate to have more than one PQ-Box type, the device template files are now common for all devices PQ-Box 300 Supraharmonic plot A firmware upgrade for PQ-Box 300 provides improved transient capture (with 410 kHz sampling)

See our HV Power website Technical Library for links to download the new software.

The PQ-Box 300 features the ability to measure and report up to the 3,400th harmonic voltage - way beyond the traditional 50th harmonic that most utilities PQ devices are capable of measuring.  It was built in response to the need to see what effect modern PV inverters and EV chargers have on the power system. Not everyone needs that capability of measurement – but serious consideration should be given to use of PQ recorders with more than the traditional 10 kHz sampling /50th harmonic measurement capability.

The risk of using a PQ logger with lower sampling speed is that the device is not going to show you high-order effects that may be present on your network. You will get a ‘filtered’ view, not showing the true picture of what equipment on your network is actually being subjected to.

As a picture is worth a thousand words, the image below shows results obtained from monitoring the same power supply (at the same time) with a 10 kHz sampling device (the PQ-Box 100, with 50th harmonic capability) and a 40 kHz sampling device (the PQ-Box 200 with 200th harmonic capability). [Unfortunately a PQ-Box 300 was not available at the time this comparison was undertaken].

PQ-Box 100 shows a pure sine wave.

PQ-Box 200 shows sine wave distortion.

Having recently being involved in delivering roll-out training for SIPROTEC 5 relays around New Zealand, we had a number of interesting questions raised by technicians and network engineers on the fine detail of the SIPROTEC 5 commissioning features. In response to these questions we have written up ‘DIGSI 5 Quick Note 0020’ which is now available on our website. For sure at first glance the ‘Quick Note’ might seem to be quite long and detailed, as it attempts to cover each of the valid combinations of the three main SIPROTEC 5 device ‘Operating modes’ and the seven possible ‘Test Suite’ functions. For each of the valid combinations we then describe how the relay responds against seven different ‘typical use’ conditions. So while the ‘Quick Note’ may not be a ‘quick’ read, hopefully it will be a resource for those who want to get full use out of these very useful features.

There’s no question - we are excited about the different commissioning features in SIPROTEC 5. We always appreciate user feedback - especially where these features have delivered better efficiency or simply where users have found them useful or even a joy to use.

If you’re a protection/design engineer or technician and any (or all) of this article sounds like gobbledygook, do give us a call. We’d be happy to visit with a SIPROTEC 5 relay and give you a demo of the DIGSI 5 and SIPROTEC 5 ‘Test Suite’. In comparison to writing lines and lines of proprietary code, the Siemens visual CFC logic and online and offline test features are a joy to see and use in practice!