In the world of oil and gas production, industrial facilities like petrochemical refineries and natural gas plants are essentially vast, intertwining chemistry experiments, with each process a critical step in the complicated whole. Like every other modern industrial operation, they depend on a steady supply of electrical power to keep the machinery in motion.

However, unlike a manufacturing plant, when the power goes out, either due to a fault on the power system or improper protective relay operation, not only do production and processes grind to a halt, but in the case of a natural gas plant the entire production run can literally go up in flames, to the tune of hundreds of thousands of dollars in lost revenue per day. As a result, most large oil and gas facilities maintain onsite power generation, with their connection to the grid serving primarily as an insurance policy. Proper protection and monitoring of onsite generation is of great importance at this type of facility.

Such is the case at Marathon Oil's Yates Field and Indian Basin Gas Plants, located respectively in Iraan, TX and Lakewood, NM. The two facilities are the premier asset bases at Marathon Oil's Southern Business Unit, explains Marathon senior engineer Charlie Adams.

According to Adams, a short power shutdown presents the very real risk of losing control of the plant processes where chemical and cryogenic processes within the plant go "off spec." Based on market values it may cost $15,000 in fuel alone, which must be purchased commercially, to restart the Yates facility. An extended power outage can also make a significant dent in production from the Yates Field, which generates about 20,000 barrels a day. At $25 a barrel that's a daily revenue stream of around $500,000 a day.

SEL Relays Solve Problems at Yates Field

Adams' power system challenges at Marathon began nearly three years ago, and involved a number of tricky problems with two main switchgear facilities. The first project was at Yates, a situation which he describes in hindsight as "frankly, a little scary."

"The Yates Gas Plant had a history of unreliable power service, and one of the things I initially struggled with was developing a solid way to measure the results of our work. One of the metrics we zeroed in on was the breaker trip frequency of the utility feeders that tie into the bus, where we have a utility tie and two generator sets that feed power into the bus. We refer to this frequency as the trip index," he says.

With paper maintenance records showing a thousand trips on the utility tie-breaker in a period of just three years, translating to about one a day, he knew the primary job was to bring the trip index down. Further investigation uncovered a messy, overlapping combination of generator control and governor control problems, reverse power trips, significant transient issues, and unreliable electromechanical relays with questionable maintenance histories. There would be no quick fix.

"The existing hardware was all pure analog devices with no historical data capture capabilities, so pinning down problems was really a series of educated guesses, since most electrical power events are so quick and there is very little evidence left behind as to what happened," he says.

The project eventually focused on replacement of the unreliable relays on the utility feeders with SEL-351 digital relays (pictured), installation of two SEL-300G generator relays, and the replacement of 34 aging electromechanical relays with new hardware from Schweitzer Engineering Laboratories, Inc (SEL).

Founded in 1984, Pullman, WA-based SEL is a leader and innovator in the design and development of power relays and monitoring technology for industrial and utility power users.

Adams first learned of SEL while working at Exxon, where utility engineer David Renfro recommended that he install an SEL-351 simply to demonstrate its abilities as a data capture device in an application.

"We put the unit in, hooked up a modem, and monitored it. It was impressive. Renfro is a mentor of mine, and as a respected utility power engineer his testimonial carried a lot of weight. When I began to ask colleagues at other companies about the product, and other utility people, the feedback was 100% positive. Not a single negative word about SEL's technology," says Adams.

Knowing that Marathon already had an installed base of another manufacturer's relay, he knew he would need compelling data to justify the switch to SEL. Calling a number of people who had used both relays, he received extremely favorable reports about SEL. He then called the electric utility in Texas that is the power supplier to the Yates plant.

Adams discovered that the utility had recently purchased a large number of breakers for their substations and the same non-SEL relays he was evaluating. Their experience was not positive, the list of negatives including a number of service and firmware problems.

"Reliability is a big issue due to the exposure a public utility has, and they made the decision to change out the other relays and go exclusively with the SEL-351 feeder management relays. When I heard that it was all the testimony I needed. When I showed my people what our local power supplier down at Yates had gone through, that was all it took. My recommendation wasn't even challenged," he emphasizes.

The retrofit of the 12.5 KV switchgear at the Yates Gas Plant was significant, and had to be orchestrated within a rigid one-week shutdown window fixed by the plant's mechanical maintenance schedule. (Pictured, Marathon's installation of the SEL-300G.)

Six months of planning and prep for the relay integration, working closely with SEL and colleagues at Marathon, anticipated every aspect of the project. In addition to removing the old relays and installing and programming the new hardware, new power capacitors were installed to stabilize the generator sets, enabling them to run more efficiently and much closer to unity.

The ultimate measure of the project's success was a fourfold improvement in the trip index. When the power system was brought back up, the trip index factor had gone from nearly 1.0 to about 0.25. Adams states unequivocally that the SEL-351s were the biggest part of the story.

Adams and his team also started collecting data that gave them the ability to look into the root causes of their problems, and to determine without question whether there was trouble on the supply side or demand side.

"Finally having legitimate data collection and reporting let us focus on smart fixes, and there have been times when we've gone to the power company and said, 'We have information here that we've captured, and we think you should see it.' The data helped us solve problems on their side of the system," he says.

Indian Basin: Applying Lessons Learned

As a result of the Yates project, which was the first application of SEL relays at Marathon, Adams received a call from the Indian Basin plant, which has a much higher exposure due to the large volume of natural gas that goes to flare during an outage. Running at production levels around 250 million cubic feet a day, if natural gas is selling at $3 per thousand cubic feet, a $750,000 a day revenue stream goes up in smoke at a rate of about $30,000 an hour, not to mention fixed facility startup costs in the neighborhood of $100,000. The plant has a more complicated power system consisting of a 480 volt bus, three turbine generators, a utility connection, and a standby feeder.

The challenge: Integrating two additional distributed generators and one 900 horsepower motor that both feed into and draw startup power from the bus. Many types of problems at the Yates plant were also manifest at Indian Basin, including phantom trips and fluttering generator controls.

Based on what Adams had accomplished at Yates, he was asked to take a look. As a result, an SEL-351 was installed on the utility feeder, but the generator relays and other aging hardware were not replaced.

"It was a tougher sell, since we hadn't quite won the confidence of the plant superintendent. He wanted us there, but he was pretty possessive of the generator controls and packages, as they were critical to the plant. He didn't want us working on anything more than what needed to be worked on," says Adams.

With success stories accumulating since an SEL-351 was installed on the utility tie, the superintendent was impressed enough with what Adams' team and SEL technology had done for plant reliability that he asked them to install an additional SEL-351 relay on his bus. Adams explains that he is currently pitching a retrofit of the generator relays, with hopes of installing the SEL-300Gs at Indian Basin as well.

"The common technology will make integrating the data we collect much easier," he emphasizes.

While SEL's roots are in the utility industry, a fact that's apparent in the design and function of their entire product line, Adams' perspective on what that means to prospective industrial users of SEL's technology is illuminating.

"On the industrial side we're on the flipside of the meter. Instead of power going out, power is coming into our facility, but their technology fits nicely anyway because power is power. A relay doesn't know a utility application from an industrial one, it only knows current, voltage, vectors, and so on."

Working directly with SEL, Adams has personally assisted SEL engineers to develop improved reporting semantics geared toward the industrial user. Another key feature of SEL technology that he values highly is remote access and monitoring capability.

"I think Marathon is typical of many industrials in that we don't have a very broad power engineering base. With just a handful of people to support power systems throughout the company, which is pretty spread out geographically, having the ability to remotely manage devices is a tremendous advantage."

He uses remote access to configure devices and access surveillance reports, typically calling the relays twice a day to check status and look at the triggers and histories for smoking guns. The result has been a number of calls to local engineers prompting them to look for possible problems.

Recently he noticed a problem with the DC batteries that power the critical trip circuits for the breakers at Yates. The battery systems are 125 volt DC, and twice a day he observed a pattern where they would cycle through an intense recharge well in excess of 140 volts before cycling back to normal levels.

Keeping an eye on the pattern for a few weeks, he was able to capture hard data demonstrating the event and pass it to the electricians, who located and fixed some problems with the charging connections.

"We provide the model for the rest of the company on the upstream side of our business, and having SEL technology entrenched here means it will eventually find its way into our other operations, including downstream petrochemical facilities. Since I've been at Marathon I've gained an awful lot of firsthand experience and knowledge that supports everything I've heard about SEL and they have earned my respect. I'm a pure industrial end user, and I will consider them for every opportunity," Adams concludes.