SYNC SCOPE
Synchronoscope
A synchronoscope indicates the phase relationship and relative frequency behaviour of two AC sources.
SLD / Schematic
Symbols · SL
Synchronising lamps
Set of lamps connected between incoming and running phases that brighten and dim with the phase difference during synchronising.
In plain English
What does Synchronising lamps mean?
Synchronising lamps are connected between corresponding phases of the running system and the incoming machine. As the phase difference changes the lamps brighten and dim, and in the dark-lamp method the breaker is closed when they are dark, showing the voltages are in phase.
A simple example
Lamps cannot show small residual voltage differences reliably, since a lamp can look dark with a significant voltage across it. They are therefore a backup or visual aid, and the drawing should show a synchroscope or check-synchronising relay for the actual permission to close.
What the drawings help you do
Identify which phases each lamp is connected across. Look for a check-synchronising relay in the closing circuit. Synchronising lamps give a visual indication; a synchroscope shows phase angle and slip direction directly.
This particular reference
Set of lamps connected between incoming and running phases that brighten and dim with the phase difference during synchronising. Synchronising lamps give a visual indication; a synchroscope shows phase angle and slip direction directly.
- Coil
- A wound conductor that can produce a magnetic field when energised.
- Phase
- One of the related AC waveforms in a power system.
- Rating
- A value stating the conditions for which equipment is specified.
Read the source: IEC graphical symbols for diagrams · Generator switchgear and paralleling controls
Schematic · SL
What it represents
Synchronising lamps are connected between corresponding phases of the running system and the incoming machine. As the phase difference changes the lamps brighten and dim, and in the dark-lamp method the breaker is closed when they are dark, showing the voltages are in phase.
Lamps cannot show small residual voltage differences reliably, since a lamp can look dark with a significant voltage across it. They are therefore a backup or visual aid, and the drawing should show a synchroscope or check-synchronising relay for the actual permission to close.
How to read it
- Identify which phases each lamp is connected across.
- Look for a check-synchronising relay in the closing circuit.
Information to show or reference
- Show lamp connections per phase
- State lamp voltage rating
- Reference check-synchronising function
A distinction that matters
Synchronising lamps give a visual indication; a synchroscope shows phase angle and slip direction directly.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
IEC graphical symbols for diagrams
IEC context for graphical symbols used in diagrams; no IEC graphic is reproduced.
Generator switchgear and paralleling controls
Public generator paralleling controls context.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
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