A Coordinated Electric System Interconnection Review—the utility’s deep-dive on technical and cost impacts of your project.

Challenge: Frequent false tripping using conventional electromechanical relays
Solution: SEL-487E integration with multi-terminal differential protection and dynamic inrush restraint
Result: 90% reduction in false trips, saving over $250,000 in downtime

A D-Curve defines the relationship between a generating facility’s real power output (MW) and its minimum and maximum reactive power capability (MVAR). PJM uses D-Curves within its Energy Management System (EMS) and State Estimator to ensure voltage stability and reliable grid operation.

For wind farms, the D-Curve must represent:

Actual plant capability (not nameplate values)
Sustainable reactive output and absorption
Capabilities achievable under normal operating conditions

D-Curves are maintained and updated exclusively through PJM’s eDART system.

PJM relies on accurate reactive capability data to:

Maintain transmission voltage within acceptable limits
Perform real-time contingency analysis
Ensure inverter-based resources contribute to system reliability

Because wind farms use power electronics and plant-level controllers, their reactive limits are often governed by inverter current limits, controller settings, voltage constraints, and transformer capability. PJM therefore requires testing-based verification rather than purely theoretical curves.

1. What is a PJM D-Curve?
A PJM D-Curve defines the relationship between a generating facility’s real power output (MW) and its minimum and maximum reactive power capability (MVAR). PJM uses D-Curves in its Energy Management System (EMS) and State Estimator to support voltage control and system reliability.
2. Are wind farms required to maintain D-Curves in PJM?
Yes. Aggregated wind facilities registered as PJM Generation Resources are required to maintain PJM-compliant D-Curves that reflect actual, sustainable plant capability.
3. How many points are required on a PJM D-Curve?
PJM allows D-Curves with 2 to 8 points, but strongly prefers 8-point curves to improve State Estimator accuracy and operational visibility.
4. Where are MW values measured for PJM D-Curves?
MW values must be measured at the low-side of the Generator Step-Up (GSU) transformer, consistent with PJM telemetry and eDART reporting requirements.
5. What reactive capability tests are required for wind farms?
Wind farms must demonstrate:

Maximum lagging (over-excited) reactive capability for MVAR injection
Maximum leading (under-excited) reactive capability for MVAR absorption

Both limits must be sustainable, not momentary.
6. Why does PJM require at least 90% turbine availability during testing?
PJM requires at least 90% turbine availability to ensure test results represent full-plant capability and are not influenced by partial or abnormal operating conditions.
7. Can theoretical inverter capability be used instead of testing?
No. PJM expects D-Curves to be supported by testing or verified operational data. Purely theoretical or nameplate-based capability is not acceptable.
8. What typically limits reactive capability during testing?
Common limiting factors include:

Inverter current limits
Plant controller capability settings
Voltage constraints at the POI or collector system
GSU transformer MVA limits
Shunt device saturation (capacitors or reactors)

Each limiting condition must be documented.
9. What happens if a D-Curve is not updated after testing?
If updated D-Curves are not submitted within required timelines, PJM may update the D-Curve using available test data to preserve system reliability.
10. Does Keentel Engineering support PJM eDART submissions?
Yes. Keentel Engineering provides end-to-end support, including test planning, data analysis, 8-point D-Curve development, and eDART-ready submission and closeout.

In 1995, Sonny Patel earned his Electrical Engineering degree from the University of Illinois. But degrees don't build legacies — action does.

For three decades, he has worked the power industry from every side of the table: 16 years as a utility engineer at Exelon/Commonwealth Edison; generation leadership across hydroelectric, industrial steam turbine, and a 9 GW renewable fleet; NERC Regional Entity Senior Compliance Engineer and Audit Team Lead, auditing some of the nation's largest utilities; and testing and commissioning lead on equipment up to 765 kV — the very top of the North American grid.Utility. Generator. Regulator. Consultant. Few engineers have seen all four seats. Fewer still have sat in them.

His experience spans nuclear, hydro, conventional generation, renewables, oil and gas, mining — and today's data centers, where he is authoring a three-book series on data center design. He is a Licensed Professional Engineer in six states and a Licensed Electrical Contractor in Florida (Unlimited EC) — he doesn't just design the work; he's qualified to stand behind its execution.Today, as Founder and CEO of Keentel Engineering, Sonny leads a nationwide team of engineers delivering substation design, power system studies, NERC compliance, and commissioning — done right, coast to coast.Three decades. Every side of the table. One standard: accountable engineering.

In 1995, Sonny Patel earned his Electrical Engineering degree from the University of Illinois. But degrees don't build legacies — action does.

Utility. Generator. Regulator. Consultant. Few engineers have seen all four seats. Fewer still have sat in them.

Today, as Founder and CEO of Keentel Engineering, Sonny leads a nationwide team of engineers delivering substation design, power system studies, NERC compliance, and commissioning — done right, coast to coast.Three decades. Every side of the table. One standard: accountable engineering.