What is a recloser?

The electrical recloser is a modern automatic switchgear, integrated

with intelligent sensors and technology to protect power lines, grid
systems as well as electrical equipment.

1. What is a Recloser?

Recloser (or Automatic Circuit Reclosers) is electrical equipment,

precision automatic switchgear device with high reliability.

Schneider Electric U type Recloser

The Recloser is equipped with smart sensors and electronics

specially designed to protect the power grid and the customer,
automatically isolating the error and recovering if the defect has
been corrected.

2. Structure of Recloser

For electrical systems, Automatic Recloser is a collection of the

following parts:

 Overload protection

 Close automatically

 Switchgear

 Control by hand
3-phase Recloser, for column installation, vacuum chamber arc
stamping, insulated by SF6 gas or solid dielectric. On the outside
Recloser has an available position for lightning protection.

Recloser components

The control unit is installed in an outdoor pole mounted cabinet

under tropical conditions, using an electronic chip, includes
functions for measuring, protecting and saving events, and capable
of allowing monitoring, control locally and remotely, and connect to
the system.

Basically, the Recloser consists of a conventional circuit breaker

with a controller that allows programming of the number of
repetitive closings according to predetermined requirements. At the
same time will measure and store important values such as P, U, I,
time of circuit break.

3. How does a recloser work

When a short circuit occurs, Recloser opens (cut-off), after a period

of time t1 (initial setting) it will close automatically. At this time, if
the problem persists, the recloser will continue to open the circuit,
after a while t2 recloser will automatically close the circuit. Just like
that, the recloser works according to the program originally set up
and the 3rd time it will completely disconnect the circuit from the
electrical system. And the number of cuts and the switching time
are programmed by the user, so it can be changed.

Recloser has the ability to repeat at least 3 times, the ability to cut
4 times before locking. The dwell time (closing time) is adjustable

4. What is the role and function of a recloser?

Recloser provides important real-time data about the line status,

such as power (A, W, VAR), voltage (V) or frequency (f) values. This
data enhances the mid-voltage grid operation, enables fault
analysis, system diagnostics, and ultimately improves MV grid
operation efficiency.

The Recloser can recognize a fault area and restore power in a

problem-free area with a fuse switch or load breaker. It can be used
on overhead distribution lines as well as in distribution transformer
stations integrating control, protection, measurement,
 communication, fault detection, on-line monitoring of closing or
opening circuit.

Functions:

 Improve SAIDI and SAIFI indices by automatically reducing outages

 Defer capital works by offering features that reduce network

stresses

 Easily integrated into Smart Grid applications with advanced

capabilities such as Loop Automation and Automatic Changeover

 Flexible applications from complex substation or standalone pole

mounted through powerful automation and communication features
Since many short-circuit cases occur at medium voltage supply
sources that are transient in nature, the recloser is a necessary
device to improve the continuity and quality of electricity in medium
voltage grids in the whole world.

5. Installation location and conditions

The Recloser can be placed anywhere on the electrical system

whose ratings meet the system requirements.

The logical locations are:

Set at the station as the main protection device of the system

Placed on the main lines but far from the station to segment long
lines, thus preventing from affecting the whole system when there is
a problem from the source.

Placed on the trunk lines to protect the mainline line from damage
caused by branch failures.
 Installation and operating conditions:

 The air temperature ranges from -450C to below + 850C

 Air humidity up to 100%.

 Maximum installation height 3000m above sea level

 Not often vigorous shaking

6. Where to buy a recloser?

In the international market, Recloser branded Schneider has been

trusted by customers for its quality and suitability for the grid.

D I S T R I B U T E D E N E R G Y G E N E R AT I O N C O N N E C T I O N U S I N G

RECLOSERS
 What is Distributed Generation (DG): Definition
Distributed Generation (DG), also Distributed Energy definition, is a quickly developing segment
of energy market and it presents a good alternative to the bulk conventional centralized power
planning. The investments in distributed generation units are largely stimulated by the
increasing demand of quality and effective power supply, social interest in Green Energy
Resources, greenhouse gas emissions reduce, political aspects and technological
developments. Finally, renewables market segment development is largely supported by
numerous governmental programs and incentives. Advantages like environmental friendliness,
expandability and flexibility made distributed power generation an attractive option for modern
and future grids. In many countries with remote clusters of loads the concept of Microgrid
appears to be a cost-effective alternative to building long transmission lines from the main
power system.

Despite all the benefits provided by the DG, there are a number of new challenges and
technical issues for power engineers who are responsible for distribution network operation,
therefore significant attention is paid to DG connection points.

DG Types
o Solar power generation – Photovoltaic (PV) systems and power stations
o Wind power generation – wind turbines and farms
o Small hydro generation – river run through or conventional type small hydro plant (up to few
tens of MVA)
o Capacity generation – diesel and gas generators used for peak shaving and grid balancing
o Energy storage systems – two way nodes that act either as load or source. Also used for power
quality purposes (power factor, harmonics, phase balancing etc.)

DG Connection Points: Examples of Applications

Connection Point Single Line Diagrams

Typically, DG connection points is represented by one (Figure 1, No1) or two (Figure 1, No2)
circuit breakers. Sometimes multiple DG electricity sources are connected to a single bus and
then connected to the main grid through additional circuit breaker (Figure 1, No3).
 Figure 1: DG Connection to the Grid

For redundancy purposes sometimes two interface breakers are used. In some cases (e.g.
large wind generation farms) multiple DG sources are connected to the ring (Figure 1, No4) or
meshed network which is then connected to the distribution grid through several connections
points.

Electrical Switchgear

Switchgear type varies from region to region and depends on many factors:

o Connection voltage
o Size (capacity) of generation
o Available budget
Types of switchgear used for distributed generation connection:

o Panel switchgear
o Ring Main Unit (RMU)
o Recloser
In North and South America automatic circuit recloser is the most common switchgear for DG
connection point. Most if not all IPPs, cooperatives and smaller Distribution Network Operators
(DNO) in USA are using reclosers to connect distributed energy to their grid (some examples:
Gehrlicher Solar, SunEdison, Progress Energy Carolinas etc.) The same goes for South Africa,
Middle East and Australia. In the UK it is a mix of reclosers, RMUs and indoor panel
switchboards used for this purpose.

Power System Protection

Due to bidirectional power flow in distributed energy generation power system, the protection
typically shall be able to distinguish between forward and reverse power flow. Thus overcurrent
and earth fault protection elements shall be directional. Protection settings engineering is
further limited by:

o Existing grid protection and margins available for time grading

o DG sources are often interfaced with power electronic converters that naturally limit the
overcurrent (that in turn makes it more difficult to distinguish between fault and load currents)
To avoid stress on the system when connecting DG to the grid Sync check feature is often
specified as a requirement for DG connection switchgear. Some customers also demand other
sophisticated protections: high impedance earth fault, broken conductor, neutral voltage
displacement etc.

Customer Problem

Targets

System integrator

o To make connections at minimum overall cost

o To execute DG projects quickly (to free resource and deal with new projects)

Independent Power Producers and Utilities

o To execute DG projects quickly (to get the maximum benefit from present government
incentives)
o To execute projects at low cost
o To ensure minimum disturbance to the network
o To ensure network protection is not jeopardized
o Quick disconnection of DG source in the event of fault (typically under 2 periods) to avoid
damage to cables and plant due to very high (above rated withstand) short circuit currents
o To provide high equipment availability regardless weather conditions

DG Problems

o Indoor panel switchgear projects have considerable execution time (more than half a year)
o RMUs require a number of additional equipment (sophisticated protection relays, voltage
transformers, communication etc.) – it leads to delays and problems with commissioning)
o Lack of engineers for protection settings calculations. As overall rate of DG connections and
DG connection inquiries is very high – many utilities are forced to outsource protection settings
calculation from external consultancies)
o Lack of resource for new switchgear and protection maintenance)
o RMU equipment is prone to floods)
o Conventional RMU is not capable to disconnect DG sources quickly (typical operation time will
be over 100 ms – and damage to the network can’t be avoided))
o Conventional RMUs have SF6 leakage problems – regular gas monitoring and costly
maintenances are required)
o Technical problems in the areas of power quality (voltage and frequency stability issues,
harmonics) and reliability)

Tavrida Electric Technologies for Distributed

Energy Generation
Tavrida Electric offers the perfect solution for DG sources grid integration - Rec15/25/35
series automatic circuit recloser 15 kV and 38 kV Triple Single and Three-Phase Gang
Operated. It serves as a complete switchgear package with advanced protection and
automation features. Additionally, Tavrida Electric provides a “Plug and play engineering”
approach to the customers - reclosers are delivered on site pre-programmed (both protection
and communication settings) and factory tested (including functionality testing). On request
Tavrida Electric also calculates protection settings for the customer.
Figure 2: Rec15 automatic circuit recloser

The Rec series recloser employs a sophisticated measurement system and special protection
elements to ensure the correct operation of DG unit. For example, Tavrida Electric was one of
the first recloser manufacturers who had implemented an undervoltage / overvoltage (27/59)
and underfrequency / overfrequency (81U/81O) protection functions. Furthermore, special
elements such as Voltage Reclosing Control (VRC), Close Condition Verifier (CCV) and
Synchronization indicator (SI) prevent potentially hazardous conditions, while Rate of Change
of Frequency (ROCOF) and Voltage Vector Shift (VVS) prevent islanding and other potentially
hazardous conditions.

All Tavrida Electric products are designed with capability of reliable communication for remote
access and supervision since this is the fundamental part of modern electricity networks. Rec
series recloser has the embedded remote telecommunication unit that provides simple
integration with SCADA over DNP3, Modbus or IEC 60870-5-104 communication protocols with
no additional expenses. Moreover, it comes with a free user software package Tavrida Electric
Automated Relay Manager (TELARM) and TELARM® Dispatcher system that works as a
standalone SCADA and / or in parallel with an existing one.

Sectionalizing various parts of electrical network with the help of a recloser is possible not only
between network utility company and DG power plant but also inside a large power plant. For
example, it is possible to combine several fields of solar panels and wind farms into a single
power system. In the event of an emergency or planned shutdown of one field of distributed
energy generation, it will not turn off the rest of the generating capacity, and distributed power
plant will continue to operate.
 Customer Advanced Benefits

Why Distribution Recloser?

o Recloser is the most cost effective way of DG connection. The recloser is available at fraction
of cost of indoor switchgear panel type (typically 20-30% when considering civils cost)
o Recloser can be installed and commissioned at a much higher pace (the whole installation,
including civils and earthing can be done in few days, whereas indoor switchgear will require
minimum 6 months to execute)
o Sophisticate protection and automation functionality is needed (including directional protection,
sync check, communication etc.) and the recloser already has all of it embedded in a single
device, whereas for RMU it is required to purchase and integrate additional modules
o Recloser can be installed high above the ground, this installation is immune to floods without
expensive flood protection

Why Tavrida Electric?

o Light weight for quicker and cheaper installation

o Maintenance free equipment – zero operational expenses
o Plug and play engineering ensures straightforward and hassle-free commissioning
o Tavrida Electric provides consultancy services on request (protection settings calculation)
Compatible with 3rd parties SCADA and provided with proprietary SCADA solution free of
charge Fastest breaker on the market1, no need to use additional fault limiting solutions
(current limiters, reactors, network reinforcement etc.)
o Compatible with SEL-65IR control module
o More than 60000 outdoor reclosers installed worldwide since 1997
Figure 3: Costs comparison

Photovoltaic plant in Romania National Grid

Connection Case

Case Description of Applying Tavrida Recloser for Solar

PV Plants

SC Energobit Tavrida SRL provided consultancy and equipment (reclosers Rec25) for the grid
connection of PV plants placed in the fields of Transylvania, or southern Romania. These plants
were placed on slopes with a southerly exposure, where the light from the sun is optimum,
transforming solar energy into electrical energy. The customer is the SPG Energy Company. It
produces, distributes and markets renewable and alternative energy resources. Tavrida
Electric’s goal was to provide a reliable solution for renewable energy investor that meets high
technological standards. This application should ensure that the power plant is interfaced with
the grid, meeting all of the high-quality requirements of utility standards for produced energy. It
should also provide solutions to the National Grid Dispatcher: the co-coordinating authority that
manages the National Electric Network.
 The renewable energy field is one of the most attractive new businesses with some of the
fastest development in recent years, and Tavrida Electric appreciates it as an excellent
business opportunity. It is also very challenging, a real test of technical and engineering
expertise, in order to meet the highest technological standards.Tavrida Electric was the first in
this market, in Romania, providing reclosers for DG connection. The biggest challenge here
was to meet the client’s requirements (more energy production) with National Dispatcher
requirements, whose primary concern is the security of the system. Our company needed to
offer a complete and reliable hardware solution that could meet these two criteria, maintain
freedom of choice to the client and offer a kind of “flexible” protection in the control cubicle.

Result and Benefits

Tavrida Electric’s solution provided a secure and reliable answer to the customer’s needs that
exactly meets the imposed utility requirements on energy production. As a result, the customer
experienced the following benefits:

o One of the lowest overall costs for DG switchgear

o Very fast project implementation (each recloser project has been completed within a month)
o Maintenance-free and environmentally friendly equipment
o Reclosers were integrated into utility’s SCADA without any problems
o Sophisticated control and protection system with directional elements