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DTR-EP
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| COMPLEX DIGITAL TRANSFORMER PROTECTION FOR
MEDIUM VOLTAGE NETWORKS |
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| The complex digital transformer protection
for medium voltage networks of type DTR-EP is part of device family named
EuroProt. This short description contains special data of this type. General
and common features of EuroProt family can be found in the EuroProt system
information sheet. Accordingly it is proposed to study both this short description
and system information sheet too, in order to understand the device entirely. |
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| Application field |
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| The DTR-EP type complex digital transformer
protection is designed to perform all protection functions of medium voltage/0.4
kV auxiliary dry type or oil insulated transformers, applied in powerplants
and in industrial plants. It contains phase and earth fault protection,
overload protection, reserve protection for the transformer and circuit
breaker protection. |
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| Main features |
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- contains all necessary protection functions
- for phase fault protection it realises two phase, two stage overcurrent
protection, consisting of a high current set high speed stage and a
low current set delayed stage
- the setting of the high set current stage does not reach over the
transformer
- the delayed stage is a positive and negative sequence voltage polarised
overcurrent protection
- the setting of which must assure that the protection reaches over
the transformer
- for earth fault protection a directional, zero sequence overcurrent
function is provided
- the earth fault directional characteristics have two characteristic
angles to be set independently and has a reset hysteresis
- the overload protection is an overcurrent protection with long time
delay
- the complex protection handles the external Buchholz (gas) protection
of oil insulated transformers
- an independent two phase, self-powered, reserve protection (KZT) is
added to the numerical part
- the device has 14 output contacts (11 NO and 3 NC contacts), 3 of
them is fix (1 NC for self test and two NO for trip initiated by the
reserve protection) 11 contacts can be freely assigned with the software
matrix
- the protection is microprocessor controlled with the exception of
reserve protection and voltage relays, the handling is performed with
the help of a menu system
- the automatics contain continuous self-check functions
Software characteristics:
- built-in self-check functions
- digital event recorder for 50 events, and an event sequence recorder
with 1 ms time resolution for maximum 300 events
- analog event records with current data
- two additional timers (T1 and T2) in connection with the software
matrix
- the rows of the matrix (the relay-functions) can be latched
Hardware characteristics:
- numerical type, with own A/D converter, digital signal processor (DSP)
and separate main processor
- 8 opto-coupler inputs
- 14 output contacts
- the type of the contacts (NC or NO) can be selected individually for
each contacts when ordering
- versions for 19" rack cabinet mounting or housed in relay case
(semi-flush mounting or hinged type)
Communication:
- 2x16 character LCD display for setting the functions, dispalying messages
and reading event records
- on-line screen on external PC to make commissioning and testing easier
- external communication interface, can be set for RS 232 or for fibre
optic cable
- optional interface module for SCADA systems
- the set parameters can be saved and downloaded
- real time clock handling with the aid of RAM with battery, (which
can be synchronised via optical fibre cable connected to external PC,
to the SCADA system, or through an optical cable)
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| Working principle |
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The scheme of working principle of DTR-EP complex
protection is shown on the following Figure. The device is a fully microprocessor
based construction, the functions and their versions are realised basically
on software.
The device contains a 87Cl96 type 16 bit micro-controller. The program is
stored in the internal EPROM of the controller, the message text for the
display is stored in EPROM as well. The parameter setting is loaded in EEPROM.
Events are recorded in battery supplied RAM. The man-machine interface consists
of a keyboard with six push-buttons, above it the two row, 2x6 character
LCD display, seven LEDs and two SW pushbuttons.
There is possibility for external communication via the RS 232 interface,
located on the front panel, or via the fibre optic cable interface on the
lower case side beside terminal block. Selection between the RS 232 or the
fibre optic is performed by parameter.
The protection contains real time clock with battery supplied RAM, synchronised
via PC or through opto-coupler input (month, day, hour, minute). The external
PC displays year as well.
The analog current inputs are connected via inductive internal measuring
transformers and low-pass filters to the multiplexer then to the A/D converter,
where all phase currents and the zero sequence current signals are sampled
in every 0,5 ms. All overcurrent stages are applied for each input current.
The protection contains the following overcurrent stages:
- two phase definite time high current set overcurrent stage (I>>)
- two phase definite time voltage polarised low current set overcurrent
stage (l> )
- zero sequence, directional, definite time overcurrent function (3Io>>)
- two phase definite time low current set overload stage (I>Overload)
- autonomous, self-powered definite time, voltage polarised overcurrent
reserve protection
The setting of the high set, high speed overcurrent function must assure
that the protection does not reach over the transformer .
The low set short-circuit overcurrent protection is a positive and negative
sequence, 0.4 kV polarised overcurrent protection. The timer of this function
starts, if the positive sequence voltage drops, or there is negative sequence
voltage component, and at the same time the overcurrent function starts
as well. The setting must assure that the protection reaches over the
transformer (I>R+I>T)*(U2>+U1<)*t.
The earth fault protection is a directional, zero sequence, definite
time overcurrent protection (3I0>,j,t).
Both characteristic angles of the directional lines can be set independently
and as it is required, and has a reset hysteresis as well. To the directional
measurement the zero sequence voltage is measured as the secondary residual
voltage of the medium voltage level voltage transformers.
The overload protection is an overcurrent protection with long set time
delay. The complex protection handles the external Bucholz (gas) protection
of the oil isolated transformers. It accepts the starting signal only
if it is at least 12 ms long, and when receiving the trip impulse, the
signal is latched until the acknowledgement in the operation menu.
The autonomous, self-powered, two phase, definite time reserve overcurrent
relay (KZT) operates independently of the digital part. In normal operation
it is blocked by positive and negative sequence 0.4 kV components so that
at submission of the trip command it takes into account the signals of
the non-digital voltage module. If the DC voltage supplying the protection
fails, then in case of operation of the reserve protection it closes the
own trip contacts without voltage checking.
The device contains continuous and periodic self-checking and monitoring
function. The continuous checking measures the presence of the supply
voltage as well. The periodic checking starts at the preset time, and
it can be started directly with the help of the menu system. Both systems
are described in details in the DKU manual. Both self-checking, system
gives alarm signal in case of the detected failure, the red LED at the
display is powered, and the LDC automatically displays an error message.
The built-in reserve protection of the DTR-EP complex protection is a
KZT type self-powered autonomous overcurrent protection. This protection
is located in an independent plug-in module of the DTR-EP device. This
protection is a classic electronic protection designed with IC technology.
Its rated current is fix, and is the same, as that of the DTR-EP protection.
There may be deviation when ordering. This device contains three induction
type intermediate current transformers. The secondary side of them supplies
partly the power consumption of the protection itself with an AC/DC power
supply unit, and they feed the electronics of the overcurrent relays (I>>
and the timers (t).)
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| Technical data |
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Rated secondary current, In
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1 A or 5 A |
| Rated voltage (line), Un |
100 V or 200 V |
| Rated frequency |
50 Hz or 60 Hz |
Overload capacity, voltage circuit, thermal, continuous
current circuit, thermal, continuous
1 s |
2xUn/Ö3
4xIn
100xIn (In=1 A), 50xIn (In=5 A) |
| Dynamic current limit |
100xIn |
Accuracy, current relays (above 50% In)
timers
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± 2%
± 3 ms (steps 10 ms)
± 12 ms (steps 1 s) |
| Reset ratio, current relays |
95% |
| Number of output contacts |
12 pcs |
| Type of contacts (NC, NO) |
1 NC, 11 NO (as requested) |
Output contacts, electrical
data:
rated switching voltage
continuous load current
making current
DC breaking capability at 220 V,
at pure conductive load
at load ofL/R = 40 ms
option at load of L/R = 40 ms |
250 V
8 A
16 A
0,25 A
0,14 A
4 A |
Auxiliary DC voltage (the same supply unit)
voltage tolerance
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220 V or 110 V
88 V to 310 V |
| Permissible ambient temperature |
0o to 50o C |
| Insulation test (IEC 255) |
2 kV, 50 Hz
5 kV, 1.2/50 µs |
| Disturbance test (IEC 255) |
2.5 kV, 1 MHz |
| Electrostatic discharge (ESD; IEC 801-2) |
8 kV |
| Burst test, (IEC 801-4) |
2 kV |
| Setting ranges |
| Positive sequence voltage relays |
(0,1-0,8)Un, step 0,1Un |
| Negative sequence voltage relays |
(0,1-0,45)Un, step 0,05Un |
| High set short-circuit overrcurent setting (I>>/In) |
250-2500%, step 5% |
| Low set short-circuit overrcurent setting (I>/In) |
50-450%, step 5% |
| Zero sequence setting (3Io>/In) |
10-104%, step 2% |
| Application of core balance CT (3Io>/In) |
10-104%, step 2% |
| Time delay t(I>>), high set short-circuit overrcurent
stage I>> |
0-1000 ms, step 10 ms |
| Time delay t( I>), low set short-circuit overrcurent
stage I> |
0-10000 ms, step 50 ms |
| Time delay t( 3Io>), zero sequence overrcurent stage
3Io> |
0-10000 ms, step 50 ms |
| Time delay t(overload), overload protection |
0-50000 ms, step 50 ms |
| Time delay t(reserve), reserve protection |
0-10000 ms, step 100 ms |
| Time delay t(BF), breaker-failure protection |
0-1000 ms, step 50 ms |
| Healthy-to-work failure signal timer, t(fail) |
0-100 , step 1 s |
| Time delay, additional timerT1, t(Mxs T1) |
0-50000 ms, step 50 ms |
| Time delay, additional timer T2, t(Mxs T2) |
0-50000 ms, step 50 ms |
| Ct rated primary current, In(AV) |
50-1250 A, step 50 A |
| External communication type |
RS 232/fibre optical cable |
| External communication speed (BaudRate) |
150 do 19200, step:2x |
| Optical fibre cable operation mode |
radial or loop |
| Daily automatic self-check time |
23 h 59 min, step 1 min |
| Automatic self-check block |
to 60 min |
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| Design, size |
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| An EuroProt device is always rack mounted, it
has two design forms. One of the form is suitable to be mounted into standard
19" cabinet frame, this form is also suitable to be mounted directly
to a relay panel with flash mounted form. The other form is a relay panel
mounted device with raised-hinged form. |
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Design
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Width
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Height
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Depth
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Rack mounting
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483 mm
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132,5 mm
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201 mm
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Panel mounting
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490 mm
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250 mm
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250 mm
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Weight 8 kg. |
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| Options |
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- digital disturbance recorder (see separate information sheet)
- SCADA connection (see EuroProt system information sheet)
- output relays with 4 A breaking capability
Information required with order
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| Information required with order |
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- Protection type [DTRV-EP]
- Output relay contact type [NC or NO]
- Protection case type
- Rated current [1 A, 5 A]
- Rated voltage [100 V, 200 V]
- Options if needed
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