The Value of a Modular Design for Protection Testing Schemes

Scott Short, Director of Protection and Automation Technology at Doble Engineering


Protection system performance testing is evolving rapidly in pace with the expanded functionalities of modern Intelligent Electronic Devices (IEDs)

Click image to enlarge

Figure 1. A modular platform can house different power sources and logical inputs and outputs to expand testing capabilities

­Power and utility companies are making unprecedented investments in substation automation and going further with implementations of the IEC 61580 standard in their substation network designs.

There are certain drawbacks to modernization when it comes to protection testing. The vast majority of protective relays in service today are either electromechanical or microprocessor-based devices that are tested by conventional analog means. Protection IEDs, however, are purely digital and are tested in virtual simulations over Ethernet. Digital testing requires a set of skills that takes time to develop. Relay testers may be too overloaded to gain proficiency with testing digitally over networks. Also, bringing digital protection applications online can lead companies to buy separate test systems specifically for testing IEDs which is expensive and can disrupt processes.

Moving forward can seem overwhelming, but the complexities can be broken down by simply identifying the features your existing test systems offer versus the features that your modernization initiatives require. The extent to which your present situation and your plans toward adopting new technologies are affected by the test systems you use depends on what you uncover when you look at your test equipment fleet strategically.

For instance, do you see an integrated platform when you look at the test instruments used in your testing program? If you operate with disparate instruments (and software) and numerous add-on accessories, it could be difficult to see how to evolve your testing program without causing more complications down the road.

Fundamentally, all protection test equipment has basic similarities, like sources and logic I/O; the differences come down to how componentry is assembled for specialized purposes, like multi-phase differential testing or high-burden electromechanical scheme testing, for example. Regardless of whether they are designed for analog, digital or hybrid analog-digital protection testing, test equipment power amplifiers, logic I/O, and control componentry are essentially modules of the instruments that house them.

Having the perspective that test hardware components are modules, it would seem they could be assembled into instruments for various test requirements without being different in terms of user experience from one test application to the next. Because of modularity, the baseline set of features could be uniform across all instruments in a fleet. The modules would be the same whether they are assembled into standard test sets or configured as specialized units.

Singular Foundation Suitable for any Testing Scenario

A modular protection test instrument allows utility teams to accommodate analog, digital and hybrid analog-digital protection schemes from a single platform.

Whether teams need equipment for routine maintenance tests or commissioning, modular platforms can be arranged to meet specific application needs, reducing complexities. As a result of varying analog sources and logic specifications for electromechanical and microprocessor relays, utilities have implemented a variety of different test sets and software to cover their testing needs. In terms of hardware, modular designs enable teams to select modules for voltage, current and logic I/O differentiations to combine into one standard instrument configuration. When utility teams can arrange and configure module combinations for any substation scenario from a singular foundation, they extend their protection testing capabilities, versatility and uniformity, reducing the need for additional instruments.

A modular test system with an intelligent command module and adaptable software at its foundation can also adjust to different substation networks and handle the communication protocols that are used without complicating the user experience. While each substation network configuration follows standards, no two substations necessarily have the same topologies or apply standards the same way. A lot of capabilities are switched between devices – typically between one or two paths – and substations can use different ranges, or parameters, concerning magnetic fields, gig speeds, redundancy protocols, and so forth. Difference in time specifications and standards being applied greatly affect the worker in the field who tests IEDs. Instead of utilizing different equipment and software depending on the network, teams using modular test systems with an adaptable command module can adjust to different topologies, timing standards and communication protocols regardless of substation category.

Click image to enlarge

Figure 2. An intelligent command module that is both forward and backward compatible can accommodate different network configurations for comprehensive analog, digital and hybrid analog-digital test cases while meeting new IEC 61580 standards

Testing substation networks based on the IEC 61850 standard requires virtual simulations over Ethernet that involve sampled values and GOOSE. Virtual testing operated via advanced software can work through the command module to isolate substation networks and present sampled values and GOOSE network traffic separately or overlayed as discrete signals. Utilities often struggle when confronting parameters involved with digital testing and new requirements that are introduced into existing testing programs that are designed around conventional relays. A command module that is both backward and forward compatible with test software for analog and digital testing enables organizations to test with virtual simulations on IEDs or test with analog simulations on conventional relays. While the hardware of modular test sets can configure to conventional substations, a command module in tandem with high-quality software enables advanced modular designs to accommodate different network configurations for comprehensive analog, digital and hybrid analog-digital test cases.

Reduces Time and Cost to Repair

By separating out protection testing specifications by module, organizations can eliminate superfluous costs and time spent on instrument maintenance and repair. No matter your level of cautiousness and preparation, relay test equipment absorbs a lot of electrical stress and parts will eventually fail, which can take time for the supplier to repair. However, an advanced modular platform offers field-replaceable modules that eliminate the need to send in the full test set. This advantage of modularity enables teams to handle simple repairs themselves and decreases downtime.

Reducing functionality loss becomes especially urgent during spring and fall outages when test set reliability is critical to keeping teams on schedule. Having the ability to easily replace modules quickly onsite avoids the possibility of an extended outage and potential revenue losses. As extreme weather events become more frequent with the acceleration of climate change, the ability to react swiftly to test instrument repairs during system restoration testing will only grow more vital.

A modular design also greatly reduces the challenges that come with replacing equipment in remote areas around the globe. The process of sending an entire replacement unit to remote international destinations when equipment fails can take months. Instead of replacing a full instrument, teams can simply have a replacement module shipped while they continue using the instrument by testing with its other available modules. This approach greatly reduces the capital needed for teams to repair the system and complete their testing.  

Adaptable to Future Conditions and Standards

With a modular design, organizations can incorporate new technology more easily and upscale their capabilities incrementally. This benefit creates a more consistent user experience that reduces disruption and time to train while allowing for more agility as digital schemes and substation automation come online and new required test practices become mandated by regulators.  

The rise of renewables is one of the major drivers that is advancing protection testing technologies. In 2020 alone, the world's renewable energy capacity growth rate increased by 45% – part of "an unprecedented boom" in wind and solar power. Wind energy alone is projected to produce 404.25 GW by 2050. However, these inverter-based power sources introduce novel fault current characteristics onto the grid which require protection testing methods to adapt to new demands for speed and selectivity. Wind and solar generation is intermittent, and the trend toward increasing these renewables on the grid will drive protection technologies to evolve as new standards and regulations develop. Investing in a modular test system that prepares you to advance your testing program non-disruptively will pay dividends as the generation profile of the power industry changes.

Smart grid implementations have enhanced the number of connections and sensors on power system networks, which has increased the potential for cyberattacks. Recent public sector interest and legislative movement brought on by major cyberattacks over the last few years indicate a future with increased security regulations in the energy and power sectors that directly impact protection testing. Maintaining compliance with NERC-CIP standards is a critical first step, but organizations need to continuously take proactive measures to protect against malware entering the substation network through transient cyber assets (TCAs) used when testing protective relays. The command module of a modular test set can work with high-quality software applications on hardened TCA field computers that are continuously updated with latest security patches and monitored for malicious code. However, cyber threats are unpredictable and growing in sophistication, meaning new requirements and standards are likely to emerge on a continual basis. A secure command module allows organizations to implement new or up level cyber protection in their protection test software to adapt to changing cyber threats and CIP standards without affecting their equipment fleet.

The versatility of modular test equipment allows organizations to slowly build their capabilities, making the transition to more modern techniques easier on the workforce and easier to implement. Organizations may purchase new or different models of equipment, but the look and feel of a modular system will remain the same, simplifying the adjustment process. As opposed to buying and learning how to use all new equipment and software, organizations can purchase new or different models of equipment while maintaining a consistent user experience, saving time they would otherwise spend on additional training.


While protection system testing has come a long way, rapid changes in the generation profile and pervasive cybersecurity threats are only accelerating the need for advanced test systems built from a modular platform.

Looking ahead, the global power industry will continue to face unprecedented challenges in its electrical infrastructure, which emphasizes the need for relay testing teams to access flexible and future-ready equipment. A modular protection testing system offers configurability for the complex testing environments of today and allows incremental changes over time from new modules and configurations. Incorporating modular test sets into an equipment fleet will provide capabilities to adapt easily to new requirements expected to come in protection system testing in the future.

Doble Engineering