EXPERIMENT IN PROTECTING THE EXCITATION CIRCUIT OF A TURBOGENERATOR FROM DOUBLE GROUNDS

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80-00809A000600260593-5
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 3
• Document Creation Date: December 22, 2016
• Document Release Date: August 4, 2011
• Sequence Number: 593
• Publication Date: November 7, 1949
• Content Type: REPORT

Sanitized Copy Approved for Release 2011/09/13: CIA-RDP80-00809A000600260593-5
COUNTRY USSR
CLASSIFICATION CONFI76NTIAL CUNF UE1T1A
CENTRAL INTELLIGENCE AGENCY REPORT
INFORMATION FROM
FnPFJrnl nCICIJMENTS OF. RADIO BROADCASTS CD NO.
SUBJECT Engineering - Electric power
HOW
PUBLISHED Monthly Periodical
WHERE
PUBLISHED Moacaw
DATE
PUBLISHED Feb 1948
LANGUAGE Russian
TWAO POC0MIAT CONTAIN% INTCNMATtON 10PSttINO I01 MATICNAL 0111001
01 TNO MSITOD ST US WIIM1M THI 510010 0r 11,1011100 ACT NO
t.. iP AND 00. AY AN1001*. ITS T11ANN5151100 00 TN0 ADOILATIOM
TS 00001715 IN ANY Mf MMON To Al OM00HOJhIOD 715500 10 PRO
Or In'.
MIORN0 0T LAW. 0i/0000 CTIOM OF 'N A.. ION. It IAONICITCD.
SUPPLEMENT TO
REPORT
THIS IS UNEVALUATED INFORMATION
Infcrmzition requested,)
EEPEL?I'63.LWT::IIL:.YSOE I6G_T$E TI0L.
CIRd5 Or~ 'D ~T -FR DL-WIZ (WOWS
fliguree are appended)
f
SOURCE Elektricheski" Stenteii, No 2, 1948.
In one of the hydroelectric stations of Moeenergo, a unique system of
protecting tae excitation circuit from double grounds was devised and installed
for a 50,000-kv generator (maul3factured by Siemens - Schuckert, with a split
stator, 1,500 rpm) having a fixed grrnend in the rotor winding at one point
(38% from the plus ring).
The protection vae caz.?ieI out by standard methods without conpeneatten
for the alternating current. The actuating?mechanism consisted of a nsTI-IIR
current relay of the ET 71/0.25 (L T ) type and a potentioaa t n= with a
resistance of 110 ohms (nom nal exciter voltage of the generator was 220 V).
The actuating current for the maximum current relay was eat ccriginally
at 0.l one. After connecting the protector in the excitation circuit of
the generator, it was established by testa that, in a balanced bridge arrange-
sent, an AC current of 100 - 130 ma flows in the relay winding causing the
contacts of the relay to vibrate. The setting of the relay :lad to be increased
teapararily to 0.3 We, but despite this the eei&oy went into operation daring
nme3mostrical short circuits in. the external network.
The flow of altcaaating current in the relay winding, as tests showed,
is caused by the presence of an induced emf in the rotor shaft of the genera-
tar which is produced by the unsymmetrical magnetic flux in the stator and
pulsations In the rotor current. Since the generator bearing on the exciter
aide to insulated from the casing, then the only closed circuit possible for
the emf induced on the o=erator shaft is the one which includes the follow-
ing: generator shaft, the point of contact of the excitation winking an the
rotor Iran, excitation winding, protective circuit, relay winding, and the
&vanding eye :i of the station.
Yung lutli I IA{(
CLASSIFICATION CORFLUMIAL
STATE NAVY DN(j NSRB I DISTRIBUTION
NO. OF PAGES
L!
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annot be carried out due to the appearance of bearing currents. The induced
emf on the exciter side of the rotor shaft has a value of about 4 - 4.5 volts.
By excluding the grounding system of the station from the protective
circuit, and by connecting the current relay directly to the rotor shaft of
the generator (specially installed brushes and cables), the alternating cur-
rent flowing through the relay was reduced from 130 to 80 ma and stray cur-
rents from the grounding system were eliminated from the relay winding.
To reduce the alternating current passing through the relay to permiss-
ible values, a locking choke coil wan inserted in eer_ee with the relay.
With a balanced bridge arrangement the alternating current flowing through
the relay as reduced from 130 to 19 ma, which permitted an increase in the
protective sensitivity by setting the relay actuating current to 120 ma.
The schema' of protection against grounds at two points (Figure 1), as
proposed by the author, is undoubtedly more reli.able than the standard type
recooananded in "Guiding Instructions on Relay Protection," and is easier to
put into practico than thy, protective circuit with AC compensation, since
the latter requires a special current transformer and a special relay with
two windings.
The choke coil can be prepared on the spot (it is possible to use, as
a choke coil, the secondary winding of a current transformer, class D or 0.5
with a transformer ratio of 2000/5, 2500/5 or 3000/5, if a reserve trans-
former is available). It is necessary that the choke coil operate with low
Induction an the iron (in the region of increasing magnetic permeabtl',y)
and high reactance of the choke coil with low effective resistance. With
the fulfillment of these conditions the choke coil reactance will increase
as the voltage across its torminals increases (Figure 2).
A satisfactory coil may be constructed using the following data:
number of turns, 400; cross-sectional area of core, 32 eq cm; and effective
resistance, 0.43 obm,'.
Figure j above how the alternating current flowing through the winding
of the protective maximum current relay, in a balanced bridge arrangement,
varies as the alternating emf increases. As can be seen from the graph, the
setting on the relay has a considerable factor of safety.
oigure, follow-.7
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CONFIDENTIAL
50X1-HUM
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 Sanitized Copy Approved for Release 2011/09/13: CIA-RDP80-00809A000600260593-5
Figure 1. gchemetitic Diagram for Protecting the Excitation Circuit of a genera-
tor From a Double Ground, With a Locking Choke Coil
100
/Se
/b
goo
700
600
SW
400
100
10
Figure 2. The Curve X=f (U) of the Locking Coil (Taken at the Cceerorclal
Frequency)
Figure 3. RelatiOnehip Between the Change in the Unbalanced Alternating Cur-
rent Flawing Through the Protective Relay and the Induced Voltage
w th MV ta1LL ---'t of the Generator
END -
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