IEEE Power & Energy Magazine - November/December 2020 - 84

ity. SCADA systems typically cover only distribution substations, and the time resolution of 2-4 s is inadequate for
capturing transient dynamics. Additionally, solar power
plants are usually located in remote areas (partially because
of the inexpensive land), which makes onsite data collection a time-consuming task for field personnel. Meanwhile,
as noted, it is of great interest to utilities to closely monitor
DER performance and ensure safe and reliable operation.
With the increasing size of solar power plants, there is a need
for monitoring and data analytics infrastructure.
To improve the visibility of solar power plants, Dominion Energy developed a solar monitoring tool to collect
disturbance event oscillography from measurement units
located at POIs. Shown in Figure 13, the system takes
advantage of cellular networks to transmit high-resolution
waveform data from solar power plants to the utility's central server. The system provides real-time alerts for system
operators so that timely actions can be taken to identify
root causes and restore outages. The monitoring system
also stores data and provides data analytics applications for

reliability of protective relays are essential; thus, most utilities
require some form of commissioning/witness testing before
connection to the system. Documentation of settings, one-line
diagrams, and test reports need to be submitted to the utility
for approval.

The Evolving Need for DER Analytics:
New Challenges Require New Tools
Increasing PV and battery penetration levels will need the support of analysis tools. Just as DER planning tools have evolved
(see Smith et al. in the "For Further Reading" section) there is
a growing need for DER interconnection and operational tools.
Here, we address several protection issues that would benefit
from a handy analytic tool. Several evolving tools will support
the assessment of DER short circuit coordination, arc flash,
effective grounding, and risk of islanding.

Dominion Energy's Solar Monitoring Tool
DERs are integrated into the distribution circuits, where,
historically, utilities have had the least amount of visibil-

PCC

Feeder 1

N.O.

Feeder 2
B

27
(3)1,000/
500:1

59
51

50N

51N
59

ANSI C37.2 Relay Devise
Function Members:

81
25

27 A, B, C = 0.5 p.u. + 12 Cycles
59 A, B, C = 1.2 p.u. + 12 Cycles
81 O/U = 60.5/57 Hz + 12 Cycles
32 R = 1.05 × Export + 15 min
79 = 10 s 1 Shot, LL + DB

M
Utility

PoC

DER Site
Draw-Out CB/Fused Switch

DER
Site
Load

AAI

IEEE 1547-2018 DER Default
Trip Limits (by ANSI):
27 - 2 = 0.5 p.u. + 9.6 Cycles
27 - 1 = 0.88 p.u. + 120 Cycles
59 - 2 = 1.2 p.u. + 9.6 Cycles
59 - 1 = 1.1 p.u. + 60 Cycles
81 O/U = 60.5/57 Hz + 12 Cycles
79 = 300 s

figure 12. The relays per ANSI Standard C37.2. Note that site relays might be integrated in inverter DERs. (Source: Southern Company Services.) AAI: active anti-islanding; PCC: point of common coupling with utility feeder; PoC: point of DER
connection; N.O.: normally open; M: meter; CB: circuit breaker; O/U: over/under; LL: live line; DB: dead bus; B: breaker.
84

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