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					                                                       Technical Information


Capacitor voltage transformers (CVTs)


                                     Type                                   Housing
                                     Capacitor voltage transformers         Capacitor units are mechanically coupled together by means of
                                     for measuring and protecion            stainless steel hardware passing through the corrosion proof cast
                                     purposes. In addition CVTs can         aluminum expansion housing. The mechanical connection also
                                     be equipped with carrier acces-        establishes the electrical connection between capacitor units. This
                                     sories to allow carrier line           facilitates field assembly of the CVT.
                                     coupling (PLC: Power line
                                     coupling) to high-voltage lines        Seals
                                     for high-frequency data trans-         The capacitor elements have oil-resistant silicone rubber double
                                     mission: CCVTs.                        gaskets. Single piece moulded O-ring type gaskets are used for all
                                                                            other sealing points.
                                     Design
                                     The CVT consists of two main           Hermetic sealing system
                                     parts: an inductive circuit hous-      Each capacitor unit is hermeti-
                                     ed in the base tank and one or         cally sealed. A stainless steel
                                     more insulators containing             diaphragm (expansion bellows)
                                     series connected capacitor ele-        is installed to preserve the inte-
                                     ments mounted on top of the            grity of the oil by maintaining
                                     base tank.                             the hermetic seal while allowing
                                                                            for thermal expansion and con-
                                     Capacitor elements                     tracting of the oil. The capacitor
                                     (inner insulation)                     units operate in a practically
                                      Capacitor elements are wound          pressure-free mode over a very                 Expansion body
                                      from alternate layers of alumin-      wide ambient temperature
                                      um foil, polypropylene film, and      range. The base tank is filled
                                      kraft paper. The capacitor            with degassed purified mineral oil and hermetically sealed from the
          Type OTCF 245               elements are impregnated with         environment and from the synthetic oil in the capacitor units. A
                                      synthetic oil distinguished for its   sight glass at the rear of the tank provides for easy monitoring of
gas absorbing qualities. Precisely controlled vacuum and tempe-             the oil level. No oil maintainance is necessary throughout the ser-
rature treatments removes gas and moisture from the paper and               vice life of the unit. An oil sampling valve is provided on the base
oil resulting in an insulation structure of the highest integrity.          tank.

Inductive element                                                           Primary Terminal
The inductive element steps down the intermediate voltage                   Several variations are available to meet customer requirements: a
provided by the capacitor elements to values suitable for relaying          vertical palm of aluminum alloy with the specified hole pattern, a
and metering purposes. The inductive element is housed in a die             line trap mounting adapter with removable HV terminal, or vertical
cast aluminum base tank with a die cast aluminum cover elimina-             stems of aluminum alloy of the specified diameter. Any of the
ting the need for painting.                                                 terminals may be nickel or tin plated solid copper.

Insulator (outer insulation)                                                Secondary Terminal Box
The outer insulation consists of high-quality aluminum oxide por-           The terminal box is very spacious to accommodate all required
celain in brown or grey according to RAL 8016 or ANSI 70 res-               connections. The secondaries of the inductive circuit (EMU: elec-
pectively (ceramic material at least C 120 according to IEC 672).           tro magnetic unit) are brought out of the base tank through an
Standard creepage distances are available according to the                  oil/air seal block assembly. Secondary terminals are housed in a
dimension tables. Larger creepage distances are available on                secondary terminal box accessible by a large lockable door. The
request. Connecting flanges made of hot-dip galvanized grey cast            secondary terminal box area is warmed by heat transfer from the
iron are bonded to the insulator by means of Portland cement.               oil filled box. This prevents condensation in the terminal box and
Upon request, a composite insulator consisting of a fibre glass             removes the need for a space heater. An aluminum gland plate is
reinforced tube and silicone rubber sheds can be provided as an             provided to accommodate customer conduit hubs. Terminal box
alternative to porcelain.                                                   protection is IP 54 according to IEC 529.
Principle circuit diagram                                                Corrosion protection
                                                                         The CVT is maintenance free and does not require painting. All
                                                                         metallic parts are corrosion-proof: housings are of seawater-
                                                                         resistant aluminum alloy and porcelain fittings of hot-dip galvani-
                                                                         zed iron. All hardware is hot dip galvanized or stainless steel. On
                                                                         request, a coat of paint with a two components paint system is
                                                                         provided. e.g. RAL 7033 (green-grey), ANSI C 70 (light grey) or to
                                                                         customer specification.

                                                                         Service Life
                                                                         No routine maintenance of the unit or oil sampling is required.
                                                                         CVTs require only a normal cleaning program for external surfaces.
                                                                         This combined with the corrosion resistance of all metal parts
                                                                         should yield a trouble free service life of more than 30 years.

                                                                         Rating Plate
                                                                         Each transformer is provided with a name plate of metallically
                                                                         anodized weatherproof aluminum or etched stainless steel.

                                                                         Grounding
                                                                         Each transformer is provided with two grounding terminals with
                                                                         two or four 14mm diameter holes. One grounding pad is located
                                                                         at each side of the unit.

                                                                         Frequency
                                                                            50 Hz or 60 Hz, other values on request.

                                                                         Dielectric loss factor / tan δ
                                                                            Less than 0.06 % / 0.0006 at rated voltage
                                                                            Less than 0.08 % / 0.0008 at power frequency test voltage
 1.   High-voltage terminal
 2.   Compensation reactor                                               Radio Influence Voltage (RIV)
 3.   MV voltage transformer                                                Less than 2500 µV at 1.1 Um
 4.   Ground terminal
 5.   Ferroresonance suppression device
                                                                         Partial Discharges
 6.   Damping resistor
 7.   Carrier (HF) terminal at CCVTs (optional)                          For the capacitor units, the partial discharge intensity is less than
 8.   Overvoltage protective device                                      5 pC at 1.2 times maximum line-to-ground voltage and less than
 9.   Secondary terminals                                                10 pC at twice the rated voltage after the power frequency voltage
10.   Link, to be opened for test purposes                               test.

Secondary windings                                                       Ambient temperature
To meet the requirements for measuring and protection, generally            -30 °C … +35 °C (24h average).
two secondary windings are provided with an option of up to four            Other values are possible on request,
windings, including the earth fault winding. The maximum burdens            e.g. -50 °C … +50 °C.
are shown in the table on the next page.
                                                                         Seismic withstand capability
Carrier Accessories
                                                                            0.5g up to type OTCF 245…
for Coupling Capacitor Voltage Transformer (CCVT)
                                                                            0.25g from type OTCF 362…
The CCVT is equipped with carrier accessories for PLC service. An           Higher value is possible on request.
external carrier grounding switch (CGS) and carrier entrance bus-
hing are provided in the terminal box. The carrier accessories           Specifications
include a carrier drain coil with protective spark gap. The drain coil
                                                                         RITZ manufactures according to all national and international
and a protective spark gap are installed in the base tank when a
                                                                         standards, such as AS, CAN/CSA, IEC, IEEE, NBN, NEN, ÖVE,
potential ground switch (PGS) is provided to prevent the loss of
                                                                         SEN, UTE, VDE and, on request, according to customers’ special
the carrier signal when the PGS is in closed position.
                                                                         requirements.
Test                                                                      Sectional drawing
Routine tests are performed in accordance with national and
international standards. Each Ritz capacitor element is routine
tested for lightning impulse, power-frequency withstand, partial
                                                                                             1
discharge, dielectric loss factor and capacitance. A test report is
provided for each unit.

Transport                                                                                    2
                                                                                                                                     11
CVTs must be transported and stored in upright position. Multi-
capacitor unit assemblies are delivered with the upper capacitor                             3
units packed in the same crate.                                                                                                      12

Installation                                                                                 4

The base unit and upper stack elements can easily be assembled
by following the instruction manual. No special tools are required.                                                                  13
                                                                                             5
                                                                                                                                     14



                                                                                             6                                       15
 1.    Primary terminal                 11. Diaphragm housing
 2.    Oil expansion diaphragm          12. HV lead of capacitor                    7
 3.    Spring assembly                  13. Porcelain insulator                                                                      16
 4.    Capacitor stack                  14. LV lead of capacitor
 5.    Intermediate voltage lead        15. Cover plate                             8
 6.    Bushing assembly                 16. Sight glass                                                                              17
 7.    Reactance protective gap             oil level indicator
 8.    Secondary terminal box           17. Transformer                             9
 9.    Seal block assembly              18. Oil sampling device                                                                      18
10.    Reactance                                                                   10



Ratings
Capacitive voltage transformers can be rated for metering and/or
protection purposes.
The following burdens (as a sum of all windings except the ground         The following capacitances are standard for the various voltage
fault winding) can be achieved.                                           levels:

                                                                                                       ...SR        ...IM           ...ER
          Type OTCF...     SR          SI      SM         IM       EM      Type (Um [kV])              ...SI                        ...EM
                           ER                                                                          ...SM
                                                                                                               Capacitance (pF) *
 Freq.        Class         Rated burden (VA) according to IEC
                                                                           OTCF    72,5...            12500        16700        37500
                0,2         25         50      100        200       230    OTCF   123...               7500        10000        22500
 50 Hz          0,5         60        120      250        500       580
                                                                           OTCF   145...               6250         8300        18800
                1,0        120        250      500        800      1000
                                                                           OTCF   170...               5250         6700        16200
                0,2         30         60      120        250       280
                                                                           OTCF   245...               3750         5000        11300
 60 Hz          0,5         80        150      300        600       700
                1,0        150        300      600       1000      1200    OTCF   362...               2630         3350         8100
                                                                           OTCF   420...               2080         2870         6250
                            Rated burden according to IEEE                 OTCF   550...               1750         2250         5400
                                                                           OTCF   765...                                         4000
 60Hz                    1.2 Z      0.6 Z     0.3 Z   0.3 ZZ    0.3 ZZ
                                                                          * other values on request
                                   Thermal burden (VA)

 50 Hz                    800         800      800        800      1200
 60 Hz                   1000        1000     1000       1000      1500
Dimensions
The following dimensions refer to standard versions.
Other Um values effect other dimensions.
                                                                                                                     Basetank
                                                                                                                     mounting pattern




 Highest system voltage (Um )           kV   72,5       123      145       170        245    362         420        550        765
 Impulse test voltage (BIL)             kV    350       550      650       750       1050   1175        1425       1800       2100

 OTCF        Creepage distance          mm   1709      3099     3721     4572        6198   9144       11163     13716
 ... SR      Dimensions mm              A    1251      1616     1824     2054        2848   3724        4715      5394
 ... SI                                 B     580       945     1153     1383         945   1383        1153      1383
                                        C     455       455      455      455         455    455         455       455
                                        D     356       356      356      356         864    864         864       864
                                        E                                             287    287       2x287     2x287
             Total weight (approx.)     kg    200       227      234       259        330    393         460       527
             weight of oil (approx.)    kg     41        43       47        52         52     58          64        69

 OTCF        Creepage distance          mm   1709      3099     3721     4572        6198   9144       11163     13716
 ... SM      Dimensions mm              A    1412      1778     1986     2215        3002   3876        4815      5535
 ... IM                                 B     580       945     1153     1383         945   1383        1153      1383
                                        C     625       625      625      625         625    625         625       625
                                        D     356       356      356      356         864    864         864       864
                                        E                                             287    287       2x287     2x287
             Total weight (approx.)     kg    257       284      291       316        386    450         550       584
             weight of oil (approx.)    kg     61        63       67        72         72     78          80        89

 OTCF        Creepage distance          mm   1631      2736     3419     4369        5471   8738       10590     13106
 ... ER      Dimensions mm              A    1286      1637     1859     2126        2890   3868        4820      5609
                                        B     545       926     1148     1415         926   1415        1148      1415
                                        C     490       490      490      490         490    490         490       490
                                        D     446       446      446      446         864    864         864       864
                                        E                                             327    327       2x327     2x327
             Total weight (approx.)     kg    257       305      327       368        484    611         830       855
             weight of oil (approx.)    kg     52        56       60        65         77     95         115       126

 OTCF        Creepage distance          mm   1631      2736     3419     4369        5471   8738       10590     13106       17475
 ... EM      Dimensions mm              A    1448      1798     2022     2289        3040   4021        4920      5756        7488
                                        B     545       926     1148     1415         926   1415        1148      1415        1415
                                        C     660       660      660      660         660    660         660       660         660
                                        D     446       446      446      446         864    864         864       864         864
                                                                                                                                           Subject to changes without notice.




                                        E                                             327    327       2x327     2x327       3x327
             Total weight (approx.)     kg    314       361      384       425        541    668         845       911        1155
             weight of oil (approx.)    kg     72        76       80        85         97    115         130       146         176
                                                                                                                                           Dimensions typical.




GERMANY:                                       AUSTRIA:                                     USA:
RITZ Messwandler                               RITZ Messwandler                             RITZ Instrument Transformers, Inc.
Salomon-Heine-Weg 72                           Postfach 25                                  One Ritz Ave.
D-20251 Hamburg                                A-4614 Marchtrenk                            Waynesboro, Ga 30830
Phone:    +49 (0) 40 / 5 11 23-130             Phone:    +43 (0) 72 43 / 52 28 50           Phone: +1-706-554-88 00
Telefax:  +49 (0) 40 / 5 11 23-286             Telefax: +43 (0) 72 43 / 5 22 85 38          Telefax: +1-706-554-88 08
eMail:    ritz@ritz-international.de           eMail:    ritz@eunet.at                      eMail:    ritz.usa@worldnet.att.net
Internet: http://www.ritz-international.de
                                                                                                                                  CVT 00       GB

				
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