ABB SYNCHROTACT®5 Operating Instructions
General information 
1.1 Introduction 
This User Manual is aimed at persons who have a basic knowledge of working with 
electronic equipment, who understand electrical symbols in schematic diagrams, but 
who know little or nothing about working with SYNCHROTACT 5 equipment. 
The User Manual provides the information required in order to install, commission and 
operate the SYNCHROTACT 5 device of types SYN 5201 and SYN 5202. 
1.2 Marking of text sections 
General warning 
This symbol placed before the text indicates situations or conditions which can cause a 
risk of death or serious injury. The text describes the procedure for preventing these 
risks.
Dangerous voltages 
This symbol indicates that, when handling the equipment, dangerous voltages occur 
which can cause death or serious injury. 
The sections of text marked with "Caution" contain information on situations which can 
lead to material damage or equipment failure if the instructions are disregarded. 
The sections of text marked with "Note" provide additional information. This must be 
taken into consideration in order to prevent malfunctions. 
Caution
Note
1.3 Purpose and use of the SYN 5201 and SYN 5202 
The digital synchronizer can be used for the following applications: 
• For automatic synchronization and paralleling of generators 
• For automatic paralleling of synchronous and asynchronous lines, transmission lines 
and busbars (incl. tap-changer matching). 
• As a paralleling monitoring device (synchrocheck) for monitoring automatic or manual paralleling sequences including dead bus.

Brief description 
The SYNCHROTACT 5 digital synchronizer is used for automatic synchronizing and 
paralleling of generators with lines and for the paralleling of already synchronous lines. 
The device is designed for system frequencies of either 50/60 Hz or 16 2
/3 Hz. 
SYN 5201 is a single-channel synchronizing device whose component choice and 
software design provides the highest security against incorrect paralleling. 
SYN 5202 consists of two independent channels with different hardware and software. 
This dual-channel property maximizes security against incorrect paralleling. 
All parameters required for paralleling are stored in a parameter set. The paralleling 
conditions and the characteristics of the voltage and frequency matchers are defined in 
this set. With the option providing seven parameter sets, paralleling can be carried out 
under different conditions or with different matcher characteristics using the same 
device. Seven configurable digital inputs and outputs are available for the selection and 
back indication of a parameter set. 
The data which are important for commissioning and for control purposes can be 
uploaded or downloaded using the PC tool SynView or, alternatively, via the keypad on 
the front panel of the unit.
The following measured variables are generated from the two single-phase measuring 
voltages: 
Voltage U1, U2 
U1 is the reference voltage e.g. line 
U2 is the adjustable voltage e.g. generator. 
Frequency f1, f2 
f1 is the reference frequency 
f2 is the adjustable frequency. 
Voltage difference ΔU 
ΔU = IU1I – IU2I 
ΔU > 0 Adjustable voltage is lower 
ΔU < 0 Adjustable voltage is higher 
Slip s %100*121fs ff − =
s > 0 Adjustable frequency is less (e.g. generator is sub-synchronous) 
s < 0 Adjustable frequency is greater (e.g. generator is oversynchronous) 
Phase-angle difference α
21 ϕ ϕ α −=
α > 0 Adjustable frequency is lagging 
α < 0 Adjustable frequency is leading 
Acceleration ds/dt 
[ ]ss dtdsxxx /%*2/
561∑==Δ=
(Every 0.5 s, an average value is formed from 56 measurements; sampling period: 9 ms) 
ds/dt > 0 Adjustable frequency is reduced (e.g. generator accelerates) 
ds/dt < 0 Adjustable frequency increases (e.g. generator is slowed down) 
With SYN 5202, the measurement is carried out separately for each channel. It is 
possible to carry out three-phase measurements in order to detect connection faults 
(rotary field, polarity) and losses of phase.

Voltage measurement (SYN 5202: channel 1) 
The two input voltages U1 and U2 are passed to the processor via high-impedance input 
resistors, differential amplifiers, low-pass filters and A/D converters.
Voltage measurement channel 2 (SYN 5202 only) 
The two input voltages U1 and U2 are passed through high-impedance input resistors 
and differential amplifiers. The signal for the amplitude value is formed from this by 
conversion and filtering . For zero-passage detection, the signal is filtered and passed 
through a comparator. The signals prepared in this way are passed to the processor via 
the A/D converter.
SYN 5201
SYN 5202
Frequency matcher with variable intervals 
The function INVERSE f changes the way the frequency matcher functions. The pulses 
are now always the same length, but the intervals are inversely proportional to the slip. 
Pulse length: adjustable by means of the parameter tp fmin: tp = tp fmin 
Pause interval: is calculated according to the following formula (can not be set as a 
parameter): 
2.2.3 Monitoring of paralleling conditions 
The monitoring of the paralleling conditions can be divided into these parallel-functioning 
blocks: 
• voltage-carrying lines 
• no-voltage lines 
Paralleling of two voltage-carrying lines 
The monitoring of the paralleling conditions enables a paralleling command (CHK 
RELEASE) if the following conditions are fulfilled simultaneously: 
• the phase-angle difference is within the tolerance band 
• the slip is within the tolerance band 
• the voltage difference is within the tolerance band 
• the voltage does not fall below minimum voltage 
• the maximum voltage is not exceeded 
• the device is in operating status (OPERATING) 
• nominal frequency deviation ≤ 5 Hz
Paralleling of no-voltage lines (dead bus) 
A special case for the monitoring is the paralleling of no-voltage lines. A paralleling 
command release is only issued if the external release signal is active and the 
measuring logic enables the release at the same time. The release by the measuring 
logic can be enabled if both voltages are within one of the permitted ranges. The dead 
bus range can be defined as permissible for one, the other or both measuring voltages 
by means of the parameters U1not, U2not and 1*2not.
The monitoring of the paralleling conditions (CHK RELEASE) releases the paralleling 
command if the following conditions are fulfilled simultaneously: 
• the releasing signal for dead bus (digital input) is issued 
• the zero voltage(s) does not exceed the set threshold U0max 
• the current voltage does not fall below the minimum voltage 
• the current voltage does not exceed the maximum voltage 
• the current zero voltage situation corresponds to a configuration permitted by means 
of U1not, U2not, 1*2not 
• the device is in Operating status (OPERATING) 
2.2.4 Command generation 
The command generation makes a distinction between asynchronous and synchronous 
sources or no-voltage lines. Two modes, one for asynchronous and one for synchronous 
sources, run in parallel, so that a source can be asynchronous or synchronous at any 
time. The paralleling command is issued in the mode in which all conditions are fulfilled 
first. 
In SYN 5202 the actuation of the paralleling relays takes place separately in both 
channels. 
Asynchronous sources 
It is called asynchronous sources, if the two lines to be paralleled (or generator and line) 
are asynchronous before the circuit breaker is closed. 
From the slip s, the acceleration ds/dt, the line frequency f1 and the set paralleling time 
t on, the command generation calculates the necessary lead angle αv by which the 
paralleling command is shifted forward in time so that the main contacts close exactly on 
phase coincidence (see following figure)