A method of determining communication time delays (T P 1, T P 2, T P 3, T P 4, T P 5) in a communication network between a local terminal and a plurality of remote terminals (R 1, R 2, R 3, R 4, R 5) within an electrical power network (20; 30) comprising the steps of: (a) selecting, in respect of each remote terminal (R 1, R 2, R 3, R 4, R 5) a calculation node (J; J1, J2, J3, J4) in the electrical power network (20; 30); (b) calculating, in respect of each remote terminal (R 1, R 2, R 3, R 4, R 5), a corresponding remote node current (i J1R1, i J2R2, i J3R3, i J4R4, i J4R5) flowing into the corresponding calculation node (J; J1, J2. J3, J4) from the said remote terminal (R 1, R 2, R 3, R 4, R 5) and a corresponding equivalent node current (i JR1_L, i JR2_L; i J1R1_L, i J2R2_L, i J3R3_L, i J4R4_L, i J4R5_L) representative of the current flowing into the corresponding calculation node (J; J1, J2, J3, J4) from the local terminal and the or each other remote terminal (R 1, R 2, R 3, R 4, R 5); (c) equating, in respect of each remote terminal (R 1, R 2, R 3, R 4, R 5), a sum of the corresponding calculated equivalent node current (i JR1_L, i JR2_L; i J1R1_L, i J2R2_L, i J3R3_L, i J4R4_L, i J4R5_L) and the corresponding remote node current (i J1R1, i J2R2, i J3R3, i J4R4, i J4R5) flowing into the corresponding calculation node (J; J1, J2, J3, J4) to zero according to Kirchhoff's first law; and (d) extracting, in respect of each remote terminal (R 1, R 2, R 3, R 4, R 5), a communication time delay (T P 1, T P 2, T P 3, T P 4, T P 5) between the local terminal and the said respective remote terminal (R 1, R 2, R 3, R 4, R 5) from a corresponding equated sum of node currents, the method being characterised in that calculating in respect of each remote terminal (R 1, R 2, R 3, R 4, R 5) a corresponding equivalent node current (i JR1_L, i JR2_L; i J1R1_L, i J2R2_L, i J3R3_L, i J4R4_L, i J4R5_L) includes: establishing an equivalent admittance (y R1, y R2, y R3, y R4, y R5) for each remote terminal (R 1, R 2, R 3, R 4, R 5); obtaining a local node current (i JL; i J1L); and utilising the established equivalent admittances (y R1, y R2, y R3, y R4, y R5) for each remote terminal (R 1, R 2, R 3, R 4, R 5) and the local node current (i JL; i J1L) to calculate the corresponding equivalent node current (i JR1_L, i JR2_L; i J1R1_L, i J2R2_L, i J3R3_L, i J4R4 _ L, i J4R5_L). (a) selecting, in respect of each remote terminal (R 1, R 2, R 3, R 4, R 5) a calculation node (J; J1, J2, J3, J4) in the electrical power network (20; 30); (b) calculating, in respect of each remote terminal (R 1, R 2, R 3, R 4, R 5), a corresponding remote node current (i J1R1, i J2R2, i J3R3, i J4R4, i J4R5) flowing into the corresponding calculation node (J; J1, J2. J3, J4) from the said remote terminal (R 1, R 2, R 3, R 4, R 5) and a corresponding equivalent node current (i JR1_L, i JR2_L; i J1R1_L, i J2R2_L, i J3R3_L, i J4R4_L, i J4R5_L) representative of the current flowing into the corresponding calculation node (J; J1, J2, J3, J4) from the local terminal and the or each other remote terminal (R 1, R 2, R 3, R 4, R 5); (c) equating, in respect of each remote terminal (R 1, R 2, R 3, R 4, R 5), a sum of the corresponding calculated equivalent node current (i JR1_L, i JR2_L; i J1R1_L, i J2R2_L, i J3R3_L, i J4R4_L, i J4R5_L) and the corresponding remote node current (i J1R1, i J2R2, i J3R3, i J4R4, i J4R5) flowing into the corresponding calculation node (J; J1, J2, J3, J4) to zero according to Kirchhoff's first law; and (d) extracting, in respect of each remote terminal (R 1, R 2, R 3, R 4, R 5), a communication time delay (T P 1, T P 2, T P 3, T P 4, T P 5) between the local terminal and the said respective remote terminal (R 1, R 2, R 3, R 4, R 5) from a corresponding equated sum of node currents, establishing an equivalent admittance (y R1, y R2, y R3, y R4, y R5) for each remote terminal (R 1, R 2, R 3, R 4, R 5); obtaining a local node current (i JL; i J1L); and utilising the established equivalent admittances (y R1, y R2, y R3, y R4, y R5) for each remote terminal (R 1, R 2, R 3, R 4, R 5) and the local node current (i JL; i J1L) to calculate the corresponding equivalent node current (i JR1_L, i JR2_L; i J1R1_L, i J2R2_L, i J3R3_L, i J4R4 _ L, i J4R5_L).