IEEE Power & Energy Magazine - May/June 2017 - 81

on the distribution system (where sensors cost more
to acquire and install) as opposed to simply obtain-
ing information from the DERs. If the utility of the
future is to operate the distribution system in real time
to manage the reliability and operational challenges
derived from DER variability and load (and, just as
important, if the system is to be engineered to allow
for that management and its associated savings), then
visibility and controllability are essential. Hosting in-
creased DER penetration levels and avoiding worst-
case distribution investments require a significant
level of real-time DER visibility.
✔ Improved flexibility, reliability, and DER hosting via
advanced distribution system technologies. The ideal
scenario for the distribution system of the future in-
cludes the ability to monitor and control, in real time,
all key components of distribution circuits. This is dif-
ficult to achieve over the short term, given the monu-
mental size and complexity of the distribution grid and
the sizable investment and infrastructure (including
communications systems) required. However, a gradual
transition toward this vision is possible and necessary
to achieve reliable, resilient, and secure service and op-
erate the complex, highly dynamic distribution grid as-
sociated with a high penetration of DERs.
✔ A well-trained workforce. New knowledge and skills
will be required to deal with a changing grid in the utility
of the future.

Future Distribution System Architecture
The key technologies at the device, substation, and system level
for distribution grid modernization include the following.
✔ Advanced sensors and management systems. These
will be required to provide cost-effective monitoring

of key electric variables, including bidirectional
power flows, voltages, currents, equipment, and DER
status as well as provide fault information to circuit
breakers and other protection devices. For instance,
the ability to control DERs on a 5-min basis will
require overall bandwidth beyond the typical capac-
ity of advanced metering infrastructure networks. It
will be essential to have enough real-time monitor-
ing of circuit conditions to provide situational aware-
ness and support applications such as distribution
state estimation. Moreover, faster, more intelligent,
and more flexible volt-var schemes (such as distribu-
tion-class, power-electronics-based static compensa-
tors) that work in coordination with smart inverters
are required.
✔ Advanced distribution and substation automation
technologies.
* Distribution and substation automation promises
enhanced grid flexibility as well as improved as-
set management that will increase asset lives, re-
duce costs, and improve reliability. However, today
only about 50% of U.S. distribution substations are
fully automated.
* Digital relays, substation automation computers, and
data concentrators, as well as gateways to SCADA
and distribution and energy management systems,
are proven, fully commercial technologies. They need
to be implemented on a large scale with full utilization
of their key capabilities.
* Intelligent and adaptive reclosers and switches oper-
ating in FLISR schemes can isolate faults in smaller
sections to support increased flexibility and improve
reliability for both traditional and distributed grids,
as shown in Figure 4.

Substation

New DA
Scheme
New DA
Scheme

Neighbor
Feeder

Neighbor
Feeder
(a)

N.C. Recloser
N.O. Recloser
(b)

(c)

figure 4. The reliability benefits (SAIDI reduction) resulting from FLISR deployment via two DA schemes using reclosers.
The colors in (b) and (c) indicate the relative magnitude of SAIDI values: areas in red have higher SAIDI values than those
in green. Plots (b) and (c) show SAIDI before and after deploying the FLISR schemes, respectively. N.C.: normally closed;
N.O.: normally open. (Source: CENTROSUR and Quanta Technology.)
may/june 2017

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