GE Mark VIe System Manual page 144

6.6.1.2 Medium-level Signals (Level M)
Medium-level signals are designated as level M. MPU signals are examples of level M signals used in the controller. These
signals consist of:
• Analog signals less than 50 V dc with less than 28 V ac ripple and less than 0.6 A current
• 28 V dc light and switching circuits
• 24 V dc switching circuits
• Analog pulse rate circuits
Note Level M and level L signals may be run together only inside the control cabinet.
6.6.1.3 High-level Signals (Level H)
High-level signals are designated as level H. These signals consist of:
• Dc switching signals greater than 28 V dc
• Analog signals greater than 50 V dc with greater than 28 V ac ripple
• Ac feeders less than 20 A, without motor loads
The following are specific examples of level H signals used in cabling:
• Contact inputs
• Relay outputs
• Solenoid outputs
• Potential transformer (PT) and current transformer (CT) circuits
Note Flame detector (GM) type signals, 335 V dc, and Ultraviolet detectors are a special category (Level HS). Special low
capacitance twisted shielded pair wiring is required.
6.6.1.4 Power (Level P)
Power wiring is designated as level P. This consists of ac and dc buses 0 – 600 V with currents 20 A – 800 A. The following
are specific examples of level P signals used in plant cabling:
• Motor armature loops
• Generator armature loops
• Ac power input and dc outputs
• Primary and secondary wiring of transformers above 5 kVA
• SCR field exciter ac power input and dc output
• Static exciters (regulated and unregulated) ac power and dc output
• 250 V shop bus
• Machine fields
144 GEH-6721_Vol_I_BP GEH-6721_Vol_I Mark VIe and Mark VIeS Control Systems Volume I
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