3.7 Interoperability, DER Interconnection, and Communication Standards and Technologies

3.7.1 Interoperability for Distribution Utilities

Interoperability - What is it and why it is important for DER & distribution utilities

Utilities in this country have for many years, been required to choose a single vendor for major purchases.  For example, when building a large turbine generating facility, an RFP is issued and multiple vendors bid.  The winning bidder gets the huge contract, but they also often get a 40 year+ marriage to that utility for operational support, consulting, spare parts and preventive maintenance on the turbine.

This philosophy, if carried into DER development and distribution equipment policies will limit competition, cause increased costs for utilities, and their customers, and ultimately restrict development of innovative products and services. 

Interoperability opens the door for multiple vendor solutions, multiple vendor competition, lower costs and innovative products and services.  Every energy policy maker, utility regulator or PUD board member should embrace interoperability, promote it, fund it and require it in utility RFPs.

Interoperability is composed of three important elements:

1. A shared understanding of the information exchanged between devices & systems

2. An agreed expectation for the response to the information exchange

3. A requisite quality of service: reliability, fidelity, and security

Shared Understanding of Information Exchanged - Develop Common Language & Methods

The Common Information Model (CIM) is a standard officially adopted by the International Electrotechnical Commission (IEC) for application-to-application interactions. It aims to allow application software and systems to exchange information about an electrical network.  IEC 61850 is the IEC’s standard information model for interactions with field equipment. This standard ensures interoperability between systems and devices as well as between devices.

Generally, the IEC CIM and the IEC 61850 standards have helped to reduce the communication issues associated with Device-to-Device and Software-to-Device communications as global manufacturers have moved in supporting that standard.  In the US, not all manufacturers and certainly not many US utilities have had their systems built to these IEC standards. 

For Example: Most utility SCADA engineers have been trained by industry or within the utility.  As a result, a SCADA-employee in a utility recruited from a related industry has their own syntax and method of doing things.  Many pieces of programming for devices in a substation or distributed generator controller is unique—a so called “one-off.”  This means that when changes need to be made by a SCADA engineer, other than the one who programmed the equipment originally, the new engineer must spend weeks going through every data point and every connection interface and programming code to understand what the original programmer did.  Then, that person must rewrite that code—still with their own method of doing things, to perform the needed functions.  The result: another “one-off” programming function in the utility devices.  Many utilities have developed their own “standards” for communication in devices, but moving from one utility to another is not standardized. The most common form of standardization for utilities is staying with the same vendor’s product lines.  That way, they require their vendor of choice to maintain interoperability of their products.

This approach is no longer sustainable with the vast numbers of vendors and products available in the DER and smart grid space.  It is no longer the least cost option.

Interoperability Standards, an agreed expectation for the response to the information exchange and a requisite quality of service: reliability, fidelity, and security

To be considered interoperable, interactions between systems, applications, and/or devices must share three things between them:

• A Shared Meaning of Content (Common Information Model)
• Properly Formatted Messages (Common Language)
• A Collaboration Agreement that Specifies the behaviors and interface (Common Agreement)

A “Standard” is a written document that specifies all three requirments, it is a technical  specification, usually produced by a Standards Development Organization (SDO).  There are three general types of SDOs that enables wide adoption of technology by multiple competing and complimentary vendors:

• Recognized standards bodies (NIST, IEC, IEEE, ANSI, etc.)
• Trade alliances (Zigbee, Wifi, OpenADR, MultiSpeak)
• Vendor (Siemens, ABB, Microsoft, etc.)

In the case of item 3, Vendors must agree to license or provide open source specifications to other vendors to allow interoperability, otherwise their communication is proprietary and requires a translation from one vender to another.

Embedded in standards or by use of co-dependent standards, the concept of quality of service, reliability, fidelity and security are key requirements in the the Standard between devices.

Interoperability Standards Maturity Levels and Standards Development Organizations

Historically, Interoperability Standards and their Standards Development Organizations, like Trade Alliances, are poorly funded and supported.  Large national and international vendors want their product concepts to be adopted as the “De-facto Standards,” that way they retain a potential revenue source for licensing to all potential competitors.  So, they either don’t participate and fund SDOs or they participate with limited cooperation or an agenda for favoring their product formats -- drastically extending the approval time-frame for any particular standard by an SDO.

As a result, it is difficult for an open Standard to reach full maturity.  Standard maturity is defined in four steps:

• Proprietary Interfaces – No Standard exists so a custom integration must be performed for devices to communicate and interoperate (Common for Inverters)
• Interface Mapping – A basic Standard is forming so that a published list of communication registers or inputs and outputs can be mapped or transformed to link with other devices. (SunSpec Alliance Standard for Inverters)
• Common Model – A more detailed Standard is formed with a common model structure of the way the data/information is organized and a standard naming convention is documented.
• Plug & Play – A Standard has reached final maturity with a published format with a Shared Meaning of Content, Properly Formatted Messages, and detailed Collaboration Agreement that specifies the behaviors/security and interface.

Plug & Play Standards are the ultimate goal to assure interoperability between systems and devices.  Getting to that level of Standard is challenging for even the best funded SDO.  That is why, more support is needed from the beneficiary of standards, such as electric utilities and their customers -- relying on vendor only support for SDOs results in poor quality standards and lack of movement to Plug & Play maturity. 

With Plug & Play maturity comes the concept of “interchangeability” between devices.  Interchangeability allows DER devices and distribution equipment to be swapped out to other vendor devices without having to undergo a major re-engineering project.  This is because the interfaces, communications, security and other functions have all been coordinated between vendors and devices.  Interchangeability allows utilities to purchase lower cost products with many vendor choices and allows easier market entry for new vendors – lowering the cost for utility customers.

There are two key recognized interoperability standards organizations that are involved with DER development.  These are a bit of an exception to the poorly funded and supported field of Standards Development Organizations.   They include:

• International Electrotechnical Commission (IEC), a non-profit, non-governmental international standards organization prepares and publishes International Standards for all electrical, electronic and related technologies.  There are IEC standards for a vast range of technologies related to power generation, transmission and distribution, all the way down to home appliances, office equipment, semiconductors, fiber optics, batteries, solar energy, nanotechnology and marine energy as well as many others. The IEC also manages three global conformity assessment systems that certify whether equipment, systems or components conform to its International Standards.  Many countries have participated in the development of IEC standards, including the US.  But not all industries in the US have become involved with the IEC.   
• Institute of Electrical and Electronics Engineers (IEEE) (pronounced “i triple e”) is another key standards-making organization that is international in scope but is primarily looked to by the US. The IEEE standards involve a wide range of industries, including not only power and energy, but biomedical, healthcare, Information Technology (IT), telecommunications, transportation, nanotechnology, and many others. In 2013, IEEE had over 900 active standards, with over 500 standards under development. Some of the more relevant IEEE standards are IEEE 1815 (commonly called DNP3) for SCADA interactions, the IEEE 1547 group of standards for DER Interconnection, the IEEE 2030 series, and the IEEE 802 LAN/MAN group of standards which includes the IEEE 802.3 Ethernet standard and the IEEE 802.11 Wireless Networking standard.

More Information on Interoperability Standards

The GridWise Architecture Council (GWAC) is a team of industry leaders who are shaping the architecture and guiding principles of a highly intelligent and interactive electric system. They have developed a structure that should lead to better communications and interoperability of systems and devices for a smarter grid by coordinating organizational, informational and technical elements for clear communications and functionality.  One of their key strategies is what is known as the GWAC Stack.  The GWAC Stack is an organizational structure that outlines the relationship of economic and regulatory policy through all the methods of communications right down to how devices are physically connected to each other. 

A key output from GWAC is the Context-setting Framework for interoperability and “Introduction to Interoperability and Decision-Maker’s Interoperability Checklist” (see Figure 15).

Figure 15 : GWAC Stack Context-setting Framework