Coal

Major Benefits Predicted From DG Interconnect Standard

Issue 10 and Volume 107.

Steve Blankinship,
Associate Editor

The first standard for interconnecting distributed generation resources with utility grids — IEEE 1547 — is being published this fall. Power Engineering recently interviewed Murray Davis, vice president and chief technology officer of DTE Energy Technologies, and one of the standard’s prime authors.

PE: How did the interconnection standard come about?

Davis: Back in 1998, a number of us involved with the subject of interconnectivity identified 29 issues related to interconnecting with electric power systems. Once the so-called “29 Issues” became widely known and accepted, people got very interested in developing a standard. One such person was Dick DeBlasio from NREL (National Renewable Energy Laboratory), who became chairman of the project. I have been involved in the standards project since Day Zero and was assigned six sections of the standard to write. Over 250 people have contributed to the development of the standard. In March of 2002, the IEEE Board approved it, and it is being published this fall. We should soon start seeing it implemented.

PE: What does the new standard do?

Davis: It provides a uniform set of technology-neutral technical requirements and tests for the interconnection of distributed resources. The big problem we had in the past was that every utility had its own requirements. Technology-neutral requirements mean that whether you have a synchronous generator, or an induction generator, or an inverter-based system connected to the power system, the technical requirements are defined. The standard’s requirements are functional and do not identify any specific kind of equipment.

PE: What doesn’t the standard do?

Davis: It does not provide system protection requirements for the generation. Those protections have been in place for 100 years. We’re only looking at the interconnection between the distributed generator and the utility system. Nor does it tell you who pays for the interconnection and the system changes required. The standard does not tell you how to interconnect, only what the requirements are. And the “how-to” is more in the application guide, which is 1547.2.

PE: That brings up a point. Are additional interconnections standards coming?

Davis: There are additional standards coming to enhance what’s there. For example: IEEE 1547.1 will describe standard performance test procedures for interconnecting distributed resources to the electric power system. I already mentioned IEEE 1547.2, which will be the application guide for 1547. And 1547.3 will be the guide for monitoring information exchange and control of distributed resources interconnected with the system.

PE: When will we see those?

Davis: It’s hard to say. Producing interconnection standards is probably one of the most complex development processes one could ever imagine because it involves so many different parties. There were more than 250 people involved representing the electric utilities, manufacturers, energy consultants, the national labs, universities and so on. So you have many diverse parties with many different special interests, including regulators and staff people of the various commissions.

PE : What’s the difference between the standard and the guide?

Davis: A standard says this is what you will do. A guide points out various alternative methods for how you might interconnect. It does not recommend any particular one.

PE: When will we start seeing benefits from 1547?

I think we’ll start seeing them quickly and the benefits are huge. The immediate benefit is that suppliers can now design a system around a set of standards everyone agrees upon. Up to now, we’ve all been fumbling around trying to meet individual requirements of each utility. Because there will be less design modifications needed for interconnection, regardless of where distributed resources are deployed, it will be a much faster implementation and interconnection. And everyone will know how the equipment will be tested. All this standardization will equate to lower costs.

PE: Can you provide an example of how 1547 will lower manufacturing costs?

Davis: Yes. Our own Energy|Now products used to specify three different sets of relays. We had to maintain inventories on all three brands and all the training manuals and keep all technicians familiar with all three in order to meet varying standards. Now, every relay manufacturer can make a relay that meets a common standard.

PE: What does the standard mean to regulators?

Davis: Utilities can use the standard as a model to follow for approval by every utility commission. As it is now, each commission has a set of interconnection guidelines and they vary greatly from state to state. This provides a model for all to follow.

PE: Does the new interconnectivity standard address utility concerns on safety and reliability? Does it mark a major milestone in utility acceptance of distributed resources?

Davis: Yes to both questions. The standard emphasizes that reliability and safety are not to be compromised. We want to make sure equipment trips off line when a fault occurs on the electric power system so that when a crew goes out to restore service, the system is not energized. We also want to make sure this stuff operates correctly so it does not reduce the reliability of service to other customers. So most utilities have supported the development of the standard because it takes less time to evaluate equipment, less time to install it and you are addressing safety and reliability throughout. That will lead to more utility acceptance.

PE: Will the standard help solve problems related to grid infrastructure inadequacies such as demonstrated on August 14?

Davis: The standard does not address the transmission or sub-transmission system. It does not address grid infrastructure deficiencies such as under-voltage conditions during peak load or overloads. It only addresses the distribution system and is only concerned about adding distributed resources to the distribution system. Having said that, I believe that greater deployment of distributed resources will improve reliability and voltage regulation and lower the overall cost to serve loads on the distribution system. It should help reduce the need for additional infrastructure capacity.

PE: Can you cite a specific way?

Davis: We build a product that is a 1 MW distributed generator that you can install in a substation. So if you have a substation transformer that is overloaded, you can move it in there on wheels and it can be interconnected very quickly. It will come on whenever that transformer is overloaded, or when a distribution circuit is overloaded, and relieve the load on the circuit. It’s a lot faster and less expensive than an additional or expanded substation. Or you may have a low voltage problem on the circuit and it would come on then. Another application might be reliability. A typical utility example might be where there are a lot of trees on the circuit and every time you have a storm, the trees get into the circuit and cause problems. With tree trimming being so problematical, there are instances where putting such a generator downstream from the problem area might be the best way to protect reliability. So if the line goes out, the generator can serve what is in effect an intentional island.