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System for monitoring an electrical system of a facility includes one or more local sensing devices, each of which is adapted to be connected to the electrical system of the facility in proximity to a respective load that receives power from the electrical system so as to make local measurements of

System for monitoring an electrical system of a facility includes one or more local sensing devices, each of which is adapted to be connected to the electrical system of the facility in proximity to a respective load that receives power from the electrical system so as to make local measurements of a voltage across the load continuity measurements of electrical-power presence at one or more points in the electrical system of said facility. A processing unit is adapted to receive and compare the local measurements to reference measurements of the voltage supplied to the facility, in order to detect a fault in the electrical system.

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What is claimed is: 1. A system for detecting voltage drops along at least one electrical branch of an electrical network of a facility connected to a main power supply, said system comprising: at least one sensing device connected to an electrical branch of said electrical network in proximity to

What is claimed is: 1. A system for detecting voltage drops along at least one electrical branch of an electrical network of a facility connected to a main power supply, said system comprising: at least one sensing device connected to an electrical branch of said electrical network in proximity to a respective load wherein said load receives power from said electrical network; wherein said sensing device comprises an oscillator for tracking the electrical signal in proximity to a point at which said main power supply enters the facility wherein said tracked signal represents the signal of an unloaded electrical branch and wherein said oscillator is at least one of the following: voltage controlled oscillator (VCO), numerically controlled oscillator (NCO); and wherein said sensing device further senses the momentary voltage level in proximity to a respective load; and wherein said voltage drop is the difference between the momentary voltage level indicated by the momentary value of the VCO/NCO and the momentary voltage level sensed in proximity to a respective load. 2. The system according to claim 1, wherein said VCO/NCO tracks at least one of the following parameters of the signal at the entry point of said electrical network: amplitude, phase, frequency. 3. The system according to claim 2, wherein said facility is at least one of the following: residential unit, office, business, vehicle, aircraft, ship. 4. The system according to claim 2, further comprising at least one processing unit coupled to at least one said sensing device, wherein said processing unit provides an analysis of the voltage drops in the said electrical network. 5. The system according to claim 4 wherein said analysis of the voltage drops in the said electrical network comprises at least one of the following: detecting the presence of electrical faults of excessive voltage drop over the electrical network defined from the entry point of the main power supply and the sensing device, distinguishing between voltage faults of voltage drop at the sensing devices due to excessive voltage drop over the electrical branch and voltage drop at the sensing devices due to fluctuations in the main power supply voltage, identifying the location of electrical faults--by identifying the sensing device related to the excessive voltage drop. 6. The system according to claim 4, wherein said sensing device is connected to an electrical socket from which a load receives the power. 7. The system according to claim 6, wherein the said sensing device comprises a communication interface, for communicating with said processing unit. 8. The system according to claim 7, wherein the communication interface conveys messages between the said sensing device and said processing unit via at least one of the following means: wired communication, wireless communication. 9. The system according to claim 8, wherein the said sensing device further comprises a continuity sensing device for detecting discontinuities of electrical-power along said electrical branch. 10. The system according to claim 9, wherein the continuity sensing device counts the number of alternating-current (AC) cycles that elapsed since electrical power was continually applied to the said sensing device. 11. The system according to claim 9, wherein the continuity sensor counts the time units that elapsed since electrical power was continually applied to the said sensing device. 12. The system according to claim 4, wherein the said sensing device comprises a plug adapter comprising: receptacles which receive a power plug of the respective load; prongs for insertion into the electrical socket; and a voltage sensor that measure the voltage between the receptacles and the prongs. 13. The system according to claim 2, wherein the said sensing device further comprises a circuit breaker, enabling the sensing device to cut off the power to the load whenever a voltage drop beyond a predefined threshold is detected. 14. A method for detecting excessive voltage drops along at least one electrical branch of an electrical network of a facility having a main power supply, said method comprising the steps of: tracking the electrical signal in proximity to a point at which said main power supply enters the facility representing the signal when the branch is unloaded; sensing the momentary voltage level in at least one point along said electrical branch in proximity to a respective load; computing the voltage drop over at least one electrical branch, wherein the computed voltage drop is the difference between the tracked signal in proximity to a point at which said main power supply enters the facility and the momentary voltage level sensed in proximity to a respective load; learning a normal behavior pattern of at least one sensing device, wherein detecting voltage drops is performed in view of deviation from the normal behavior and in view of predefined limits; obtaining continuity-values from at least one continuity sensor connected to at least one electrical branch; comparing the obtained continuity values against values obtained from reference historical measurements.