UfE ENS31 Technical specifications

ENS31 Automatic Isolation Unit
Product Description
Issue 09/2005

Page 2 of 20 Product Description ENS31 Version: A.02
Issue: 20.09.2005
UfE Umweltfreundliche Energieanlagen GmbH
Joachim-Jungius-Straße 9
D–18059 Rostock
Tel.: +49 3 81 / 405 97 05
Fax: +49 3 81 / 405 97 03
E-mail: [email protected]
web: www.ufegmbh.de
Note
If you have any queries and need to contact UfE GmbH, always have the
serial number close to hand in order to make reference to it. We do not
claim the documentation is free of errors and mistakes. Please inform
UfE GmbH of any errors found in the documentation.
© Copyright
This Product Description is the copyright of UfE GmbH.
This manual is intended for the customers and project planner. It contains
instructions and information which must not be copied, distributed or
transferred by technical data methods nor used for the purpose of compe-
tition, either as an entirety or as extracts, without the necessary authorisa-
tion.
Contravention could lead to prosecution and obligation to pay damages.
All rights reserved, particularly in the case of patent application or other
registrations.
We reserve the right to make technical modifications without notice.
Note
The ENS31 isolation unit and the measuring method are protected by
patent.

Table of Contents
Version: A.02 Product Description ENS31 Page 3 of 20
Issue: 20.09.2005
1 Purpose of the Product..........................................................4
2 System Description ................................................................5
2.1 Principles of functioning..................................................5
2.2 LCD displays and LEDs..................................................6
2.3 Connections ...................................................................7
3 Behaviour of the Isolation Unit..............................................8
3.1 General information........................................................8
3.2 Fluctuations in the mains power supply..........................8
3.3 Deviation of the mains power frequency.........................9
3.4 Impedance jumps ...........................................................9
3.5 Influence of isolation units on each other .....................10
3.6 Optimised impedance measurement process ..............10
3.7 Automatic calibration of the impedance measurement.11
3.8 Automatic adaptation of switching thresholds to the
mains power conditions ................................................12
3.9 Automatic synchronisation / limitation of signal strength
in the case of frequent use of the ENS .........................13
4 Installation.............................................................................14
4.1 Mechanical installation .................................................14
4.1.1 Transport and unpacking .............................14
4.1.2 Conditions for installation ............................14
4.1.3 Preparing the electrical/meter cabinet .........15
4.1.4 Mounting on the top hat rail .........................15
4.2 Electrical connections...................................................16
4.2.1 Basic configuration ......................................16
4.2.2 Demands of the switching elements ............16
4.2.3 Circuitry .......................................................17
5 Advantages for the Customer .............................................19
6 Technical Data ......................................................................20

Chapter 1
Purpose of the Product
Page 4 of 20 Product Description ENS31 Version: A.02
Issue: 20.09.2005
1 Purpose of the Product
The automatic, three-phase isolation unit is an automatic switching unit
used to connect decentralised power generators safely to the public elec-
tricity supply.
The ENS31 isolation unit has been conceived as an independent unit for
monitoring 3-phase power feeding systems. It prevents uncontrolled island
effects following failure or shutdown of the public electricity supply.
The ENS31 complies with DIN VDE 0126-1-1 and is approved as a sub-
stitute for manual isolation devices up to a 30 kW feeding power.
By implementing this automatic isolation unit, it is possible to dispense
with a manual isolation unit which must be accessible to the public elec-
tricity supply authorities at all times.
The feeding systems can be:
•photovoltaic systems,
•small hydroelectric power stations,
•block-type thermal power stations,
•fuel cells,
•small wind energy plants.

Chapter 2
System Description
Version: A.02 Product Description ENS31 Page 5 of 20
Issue: 20.09.2005
2 System Description
2.1 Principles of functioning
The ENS31 automatic isolation unit continually monitors
•overvoltage and undervoltage
•frequency deviation
•impedance jumps
in the public electricity supply.
In the event of faults in the mains supply, the ENS31 interrupts the feed-
ing of electricity in the mains to prevent island effects.
The contact-based disconnection is initiated by externally provided con-
tactors with positively driven NC contacts. These contactors are controlled
in two channels by the ENS31 via relays Rel1 and Rel2. Request for the
switching status of the external contactors occurs via two acknowledge-
ment inputs.
After switching on, Contactor 1 is activated first and Contactor 2 is only
enabled after reaching and testing the switching status.
Note
The ENS31 cannot be switched on without the acknowledgement inputs
being correctly wired.
The safety functions are executed in a 3-channel system, whereby each
channel measures the mains voltage, mains frequency, mains impedance
and the voltage of another channel independently.
The channels monitor each other mutually (refer to the error protection in
accordance with DIN VDE 0126) to increase error protection. Therefore,
recurrent tests can be dispensed with.
Note
Further information on the principles of functioning is available on our
Internet site at www.ufegmbh.de.

Chapter 2
System Description
Page 6 of 20 Product Description ENS31 Version: A.02
Issue: 20.09.2005
2.2 LCD display and LEDs
The following indicators are mounted on the front side of the ENS31:
X XXXXX
AB
C
D
A) LCD
The unit and mains power status is shown on a 2-line LC display. Each
line can display 16 characters.
B to D) LEDs
In addition to the LCD, the unit and mains power status are also indicated
by three LEDs (red, green, yellow)
(B = L1, C = L2, D = L3).
Note
The meaning of the indicators is described in the Operating Manual.

Chapter 2
System Description
Version: A.02 Product Description ENS31 Page 7 of 20
Issue: 20.09.2005
2.3 Connections
The following connections are provided at the top edge of the ENS31:
<RELAIS
1 234
<KONTAKTE
12
<NETZ
NL1L2L3
AB C
A4 connection terminals for contactor control, potential-free,
B2 connection terminals to connect positively driven auxiliary contacts,
C4 connection terminals to connect three phases and the neutral
conductor.
Note
The connection of the unit is described in the Installation Manual.

Chapter 3
Behaviour of the Isolation Unit
Page 8 of 20 Product Description ENS31 Version: A.02
Issue: 20.09.2005
3 Behaviour of the Isolation Unit
3.1 General information
The ENS31 monitors the mains power supply and prevents uncontrolled
island effects developing in the event of a power failure or the mains be-
ing switched off.
It reacts to fluctuations in:
•voltage,
•frequency,
•impedance
of each individual phase.
Note
The default settings can be changed, if necessary. The ENS manufac-
turer must be informed of these requirements, however, prior to con-
figuration.
3.2 Fluctuations in the mains power supply
The threshold values for the mains power supply are set as follows:
Fluctuation Threshold value Test interval
Overvoltage 300 V Every 20 ms
(fast shutdown)
Overvoltage 264 V Every 200 ms
Undervoltage 130 V Every 20 ms
(fast shutdown)
Undervoltage 184 V Every 200 ms
Disconnection from the mains is also triggered when the 10-minute aver-
age value of the mains supply exceeds the setpoint value of 230 V by
more than 10% (testing the mains quality).

Chapter 3
Behaviour of the Isolation Unit
Version: A.02 Product Description ENS31 Page 9 of 20
Issue: 20.09.2005
3.3 Deviation of the mains power frequency
The testing of the frequency of the public electricity supply is completed
by all three channels independent of each other via a protective resistor di-
rectly in the mains power supply.
The threshold values for the mains frequency are set as follows:
Fluctuation Threshold value Test interval
Overfrequency 50.2 Hz Every 200 ms
Underfrequency 47.5 Hz Every 200 ms
Channel 1 also measures the phase position between the outer conductors.
In the event of a phase difference in excess of 30 degrees, the feeding
point is disconnected from the power supply.
If the rate of change of the frequency (RoCoF) exceeds 1 Hz/s, discon-
nection from the supply is also triggered.
3.4 Impedance jumps
All three channels measure the mains impedance. The time-dependent
change of voltage near the crossover (phase shift), caused by test signals,
with various voltage values forms the basis for calculating the mains im-
pedance.
All the impedances measured in one second are used to establish an aver-
age value. The number of measuring pulses is dependent on the number of
ENS connected in the network.
Depending on the power characteristics, the triggering threshold for an
impedance jump is adapted between 1 ohm and 0.2 ohm.
Note
A threshold of 0.5 ohm is set ex works.
The automatic adaptation of the switching threshold is described in Sec-
tion 3.8.

Chapter 3
Behaviour of the Isolation Unit
Page 10 of 20 Product Description ENS31 Version: A.02
Issue: 20.09.2005
3.5 Influence of isolation units on each other
When isolation units of the type ENS31 are used, they can be imple-
mented in dense proximity in the public electricity supply without it lead-
ing to operational problems. Even in the case of long network spurs and a
mains supply subject to frequent faults, unproblematic operation can be
guaranteed.
The ENS31 automatically adapts to these difficult power supply condi-
tions. To achieve this, the following processes are integrated in the
ENS31:
•optimised impedance measurement process,
•automatic calibration of the measured impedance change,
•automatic adaptation of switching thresholds to frequent fluctuations
and interference levels
•automatic synchronisation and limitation of signal strength in the case
of frequent use of the ENS
3.6 Optimised impedance measurement process
The optimised impedance measurement process improves the resolution
and interference resistance of the impedance measurement on a large
scale. Centralised ripple control signals and frequency converters hardly
influence measurements.
An island effect is recognised by a sudden increase in the mains power
impedance.
phase shift
measured by
the ENS
test signal
island formation
local power supply
average vo
l
tage supp
l
y
ENS

Chapter 3
Behaviour of the Isolation Unit
Version: A.02 Product Description ENS31 Page 11 of 20
Issue: 20.09.2005
3.7 Automatic calibration of the impedance measurement
A precision resistor in the ENS performs an automatic, continuous cali-
bration of the impedance measurements and, at the same time, a continu-
ous, automatic self-test. Manual calibration is no longer necessary.
To complete the calibration, the precision resistor is electronically bridged
several times per second and the resulting impedance changes used as a
reference for the calibration.
ENS
mains

Chapter 3
Behaviour of the Isolation Unit
Page 12 of 20 Product Description ENS31 Version: A.02
Issue: 20.09.2005
3.8 Automatic adaptation of switching thresholds to the mains power
conditions
A distinction can be made between an overreaction of the ENS and an un-
controlled island effect. In the case of an overreaction by the ENS, the
power supply remains available after disconnection of the feeding point
from the mains.
If an overreaction is detected, the switching threshold for the next shut-
down is adapted to a value which is a little above the current threshold
value that has lead to a shutdown.
Before the switching threshold is adapted to a less sensitive value, the
ENS31 switches off briefly in order to check whether the power supply is
still available. The threshold is only changed to a less sensitive value
when it is recognised that the situation does not concern an uncontrolled
island effect. In the case of stable, undisturbed mains supply feeding
points, the switching threshold is slowly set to a value (i.e. over several
days) which is about double that of the recurrent fluctuations which oc-
curred (safety clearance). As a result of this automatic adaptation to the
mains power conditions, safety is considerably increased without limiting
the availability of the system.
If the interference level repeatedly exceeds the switching threshold, the
switching threshold is incremented and the slow adaptation begins again
from the start.
switching threshold
interference level

Chapter 3
Behaviour of the Isolation Unit
Version: A.02 Product Description ENS31 Page 13 of 20
Issue: 20.09.2005
3.9 Automatic synchronisation / limitation of signal strength in the case
of frequent use of the ENS
A “team” of parallel connected ENS units at the same feeding point gen-
erate a joint, stronger test signal through synchronisation. This enables
even higher measuring accuracy. Faulty triggering is practically zero and
operation is more stable.
The parallel connected ENS units generate a “decentral test tone”. As the
number of ENS devices increases, more and more enter a passive operat-
ing state. They only generate a few signals themselves and use the jointly
generated test signal as a pilot tone which can be measured at the mains
power connection point.
local power supply
ENS
ENS
ENS

Chapter 4
Installation
Page 14 of 20 Product Description ENS31 Version: A.02
Issue: 20.09.2005
4 Installation
Danger
This chapter only serves for informative purposes. The actual instal-
lation must be performed according to the instructions in the Installa-
tion Manual enclosed.
4.1 Mechanical installation
4.1.1 Transport and unpacking
When transporting the ENS31 isolation unit, pay attention that it is always
protected against contact with dirt and damage through impacts and set-
ting down too hard.
Remove the ENS31 from the transport packaging and pull off the protec-
tive foil, if necessary.
After transport and before installation, check that the ENS31 isolation unit
is in a perfect condition.
4.1.2 Conditions for installation
The ENS31 is intended for installation on a top hat rail in an electrical
cabinet or in a meter cabinet. It cannot be installed anywhere.
The cabinet must be sufficiently large to house the ENS31, providing the
necessary contactors, protect the unit from moisture, dust, dirt and heat.
If there is not enough space in the cabinets available, a separate electrical
cabinet must be mounted to accommodate the ENS31 and contactors.
Attention
Never position the electrical cabinet containing the ENS31 above or in
the vicinity of a heater. Ensure sufficient ventilation.
The ENS31 should be mounted as near as possible to the mains power
outlet and as far as possible from the electricity feeding source.
Note
These measures reduce the effect of the voltage increase by the current
source.

Chapter 4
Installation
Version: A.02 Product Description ENS31 Page 15 of 20
Issue: 20.09.2005
4.1.3 Preparing the electrical/meter cabinet
Determine the installation position of the ENS31 on the top hat rail.
Saw a cut-out in the cabinet cover at the installation position of the ENS31
so that you can see the ENS31 and its indicators (LCD and LEDs) without
opening the cabinet.
The cut-out must have the following dimensions:
X XXXXX
219 mm
74 mm
4.1.4 Mounting on the top hat rail
Set the isolation unit with its top housing holder (A) on the top hat rail and
turn it downwards against the top hat rail (B). Use a little force to press on
the bottom housing section until the housing holder engages in the top hat
rail
A
B

Chapter 4
Installation
Page 16 of 20 Product Description ENS31 Version: A.02
Issue: 20.09.2005
4.2 Electrical connections
4.2.1 Basic configuration
The switching elements of the automatic isolating device (e.g. contactors)
are not enclosed with the unit and must be brought by the installation
technician. The technician decides on the switching elements most suit-
able.
Danger
The installation technician must ensure that the power generator is
only connected to the mains via the two switching elements assigned to
the ENS. Risk of accident!
The ENS31 must be protected by pre-fuses in the mains feed circuit (min.
6 A, max. 25 A). Observe the circuit diagram.
4.2.2 Demands of the switching elements
Two contactors with positively driven auxiliary contacts are required for
mains disconnection. The acknowledgement contacts must be connected
in the correct sequence (refer to circuit diagram).
The contactors must be designed for the nominal output of the current
inverter or the system at AC3. The decisive factor for dimensioning is the
phase with the highest load.

Chapter 4
Installation
Version: A.02 Product Description ENS31 Page 17 of 20
Issue: 20.09.2005
4.2.3 Circuitry
Check that the mains power lines and power feed lines are not conducting
electricity.
Switch the power generator (feeder), ENS31 and contactors as follows:
FEEDER
UfE - ENS31
R1R2R3R4
RELAY
K1 N L1 L2 L3
MAINS
L1
L2
L3
N
MAINS
min. 6 A
max. 25
A
***
21
22
-K10.1
-K10.1
43
21
65
43
21
65
A1 A2
CONTACTS
K2
21
22
-K10.2
A1 A2
-K10.2
Note
The additional pre-fuse (*) is only necessary if the direct mains power
fuse protection exceeds 25 A.

Chapter 4
Installation
Page 18 of 20 Product Description ENS31 Version: A.02
Issue: 20.09.2005
The terminals on the ENS31 are arranged as follows:
relay
contacts
mains
Attention
The ground conductor should always bypass the unit. The neutral con-
ductor MUST be connected to the ENS31 otherwise the unit may be
damaged.
If the ENS31 is switched on and off by means of a system control unit, the
L1 connection of the ENS31 can be switched by means of a relay.
Note
When switching on via L1, the delay until the contactors are activated
can be up to 30 seconds because the ENS31 must test the power feed
conditions again.

Chapter 5
Advantages for the Customer
Version: A.02 Product Description ENS31 Page 19 of 20
Issue: 20.09.2005
5 Advantages for the Customer
Customers have the following advantages:
•simple connection, easy installation,
•high degree of safety through monitoring voltage, frequency and im-
pedance jumps,
•high degree of reliability through automatic, continuous calibration of
the impedance measurement,
•continuous automatic self-test of the isolation unit,
•replaces the isolation unit provided by the public electricity supplier
which must be permanently accessible,
•avoids inadvertent triggering through automatic adaptation of switch-
ing thresholds to the mains supply conditions,
•minimum energy consumption, minimum heating up,
•automatic, maintenance-free operation without recurrent tests,
•automatic synchronisation and limitation of signal strength following
frequent use (several ENSs in local mains power supply).

Chapter 6
Technical Data
Page 20 of 20 Product Description ENS31 Version: A.02
Issue: 20.09.2005
6 Technical Data
Switched power (max.) Dependent on the contactors
assigned
Own consumption 3.5 W
Housing Plastic, suitable for assembly on
the top hat rail
Overall dimensions (W x H x D) 220 mm x 111 mm x 80 mm
Cut-out dimensions (W x H) 220 mm x 73 mm
Ambient conditions - 20 °C to + 40 °C,
10 to 90 % relative humidity,
non-condensating
Nominal current of power feeder According to max. switching
power of the contactors
The unit disconnects the mains under the following defined condi-
tions (complying with standard DIN VDE 0126):
Overvoltage
(fast shutdown)
> 300 V (response time 0.02 s)
Overvoltage > 264 V (response time 0.2 s)
Overvoltage (average) 230 V + 10% over 10 minutes
Undervoltage
(fast shutdown)
< 130 V (response time 0.02 s)
Undervoltage < 185 V (response time 0.2 s)
Frequency deviation + 0,2 Hz / -2,5 Hz
(response time 0.2 s)
Impedance jump detection > 0.5 Ohm (response time 0.5 s)