Determines the active source for the Electrical Study. Possible values for this property are -1 - stNone: None (default), 0 - stActiveSource: Active Source, 1 - stScada: SCADA, 2 - stOperator: Operator, 3 - stCCLink: Control Center, 4 - stBilling: Billing, 5 - stCalculated: Calculated, or 6 - stDatabase: Database. The selected source type must exist in the Analog Measurement to be set as an Electrical Study input. If this property is set to 0 (zero, Active Source), it follows the configuration performed in the ActiveSource property. Users cannot select type 0 (zero, Active Source) if the ActiveSource property is set to 100, 101, 102, 103, 104, 105, or 106 (Electrical Study outputs). In case the selected source is deleted, this property assumes a value of -1 (minus one, None).