The technology of the smart grid has been shaking up the power industry for a long time. It has been changing every aspect of how the power delivery industry operates. So long in fact, it would be reasonable to assume the grid has seen it all, and the industry has integrated advanced digital technology into every corner of the grid. It would be safe to say the transformation had reached its apex, except that isn’t exactly correct.
There are still unexpected discoveries to be made, and that’s what keeps our industry interesting. Let’s look a little deeper into the substation’s modernization activities. These facilities have truly become a technological hub as digital technology has been integrated into all the components and apparatuses, turning them into intelligent electronic devices (IEDs).
Advanced computer systems and sophisticated software combined with IEDs have merged information technology (IT) with operational technology (OT). The result was a linking of the real and virtual worlds into cyber-physical systems, but surprisingly in the midst of all of this technological transformation there is an element that is literally on the cusp of modernization.
Bucking the Trend
The substation’s auxiliary power system is one of those legacy systems that has been slow to embrace the trend toward digitalization. It has remained pretty much unchanged over the years, but that is increasingly changing. To make sure everyone is on the same page, the auxiliary power system is the electric power scheme that provides an alternate power source to the substation.
In other words, it’s a backup supply for the primary power system. The system consists of both an alternating current (AC) power and a direct current (DC) power, but it is the DC portion that is of interest. In the simplest terms, the DC system consists of a battery, a charger, distribution system, and other components necessary for safe operation, but the battery and charger are transforming.
This system is essential for providing power to the protection, control, and monitoring (PCM) system. It also powers equipment such as circuit breakers, SCADA (supervisory control, and data acquisition), and communications equipment, which are vital systems when it comes to safely supplying power to the customer. In a nutshell, without DC power the PCM system doesn’t work; breakers don’t trip, faults go undetected, and bad things can happen to good substations. That is why it is hard to understand how this critical system has been omitted from the modernization process for so long.
That doesn’t mean equipment like the batteries themselves or the battery chargers are not highly digitized and using state-of-the-art elements. There are add-on battery sensors that can provide real-time data for better utilization of the DC power system, but there are also traditionalists who prefer older methods. These folks haven’t been taking advantage of all that modern technology has to offer.
It is very similar to how dynamic line rating technologies have been disregarded in favor of the old-school static rating methods. It’s an example of technology versus comfort levels. The problem is the price everyone is paying for these overlooked capacities (see T&D World’s “Charging Ahead” December 2019 for details).
Let’s get back to the subject of substation batteries and chargers. Many utilities are still relying on long-established practices that involve a physical presence in the substation. These are calendar-based systems that require personnel, check lists, and manual test equipment to determine the health of their DC power assets. Unfortunately, there are examples showing where missed maintenance items have resulted in prolonged blackouts because the substation’s battery was compromised when called upon to operate, but that’s another story.
It Got NERC’s Attention
A few years ago, NERC (North American Electric Reliability Corp.) published their “Protection System Maintenance” requirements in their PRC-005 standards. Since the substation DC power systems are so critical and have a history of benign neglect, NERC has included the substation battery system in the PRC-005 standard. This standard not only defines the maintenance and monitoring activities, it sets the maintenance and inspection schedules for the substation DC system.
The PRC-005 standard also requires the utilities to document and retain evidence of these activities such as supply voltage, battery float voltage and current, string continuity, inter-cell connection integrity, cell ohmic values, unintentional grounds, and electrolyte. There is a great deal of expensive hands-on labor involved if the old-school approach is utilized, and failure to comply can result in monetary and non-monetary sanctions.
Talking with Andy Keels, principal engineer for kEElectric Engineering, PLLC revealed some interesting conditions and concepts when it comes to managing batteries and battery chargers in accordance with NERC’s requirements. Keels has been working as a consultant for LaMarche Manufacturing Co. to develop a smart battery charger and wanted to share some insights.
Keels said, “When it comes to efficiently implementing NERC’s PRC-005 standard, the key is to work smarter not harder. Taking advantage of automation technology is a key for doing that. There are a lot of battery monitoring systems available in the marketplace, and they do an excellent job of monitoring. Adding automation technology (i.e., sensors, transducers, etc.) to the battery charger gives it the ability to do something about a problem.”
“This technology can take the guesswork out of determining a battery’s state of charge and state of health,” Keels said. He went on to say, “This technology can identify when the battery is having problems that might affect the DC system’s reliability. It can tell things like when the electrolyte level is low, off gassing excessively, or a cell is not charging properly. However, most of the monitoring systems currently available have no way to respond other than sending someone an alarm.”
Continuing, Keels said, “These systems only report problems, but cannot correct the situation. When you think about it, monitoring something with have no way to respond to an alarm makes little sense. In effect, it can make every alarm an emergency, which results in rolling assets to the station. That is an expensive solution especially if the utility has a large number of stations or the battery is in a remote location requiring hours of drive time each way.”
According to Keels, “This is where a smart battery charger makes a difference. It can eliminate all the time consuming trips necessary to perform the routine maintenance required by NERC’s PRC-005 standard, without an additional battery monitoring system. It can also increase a substation’s DC
system safety and reliability, by correcting common problems automatically.”
Keels explained, “A smart battery charger has a microprocessor control with the ability to measure the DC system’s operating condition, data-log events, communicate operating data and events, and take action to mitigate problems automatically. Many battery problems are caused by factors that can be managed by a smart battery charger. In many cases, a smart battery charger can slow the progress of problems, or in some cases actually correct them.”
Keels concluded, saying, “A smart charger eliminates the most expensive tasks associated with NERC PRC-005 compliance. It can mitigate common problems, so the utility can respond as a normal maintenance issue rather than an emergency. It also provides the user with real-time state of charge and state of health information.”
The Next Step
Smart chargers are available from suppliers like HidlePower, iTECH, LaMarche, SBS, Schaefer, and others, but the trickledown effect is also taking place. Large utility-sized battery storage systems have been using a more sophisticated approach to managing their battery storage systems. It’s called a battery management system (BMS) and it’s slowly finding its way into the substation. BMS take advantage of battery sensors, battery monitoring systems, and smart chargers combined with advanced computing methods, big-data analytics, artificial intelligence, and other digital technologies.
BMS provide cell balancing, battery state of health, battery risk factor, state of charge determination, which protect the battery (cells) from damage, and prolong the battery’s life. With all the development going on in this area, BMS platforms are starting to attract attention. These BMS schemes take advantage of machine learning and algorithms to identify battery deterioration, predict failures, and schedule routine maintenance responses.
Smart grid manufacturers such as GE Energy, Hitachi ABB, Mitsubishi Electric, Siemens, and others are adding BMS technology to their advanced asset management systems. Suppliers such as BTECH, Eagle Eye Power Solutions, Nuvation Energy, SBS Storage Battery System, Schneider Electric, and others are providing specific BMS gear.
Stationary battery systems can be easily overlooked, but they are one of the most critical substation assets. They are essential for the operation of the protection and control schemes of substations. For utilities to efficiently comply with NERC’s PRC-005 requirements, they must change their approach to maintenance and testing of their battery systems. BMS technology is a logical extension to asset management. It offers a solution, but BMS requires a break with tradition —are we ready!
