This paper investigates the efficacy of the joint and separate methods of allocating harmonic emission limits defined in the IEC and the VDE AR-N German technical reports. Both methods are applied in a test network with 380 kV, 220 kV and 110 kV voltage levels. Based on the allocated emission limits a harmonic load flow is performed to calculate the resulting harmonic voltage levels at all nodes. A Monte Carlo Simulation is applied in order to consider the probabilistic aspect of concurrency and phase angle diversity. Moreover, various network scenarios are tested, which include different types of generation (modular multilevel converter / synchronous generator) and different aggregated medium voltage network equivalents. The harmonic voltages calculated at each node are then compared with the planning levels, in order to analyse the efficiency of the methods with respect to the different voltage levels. It can be shown, that due to resonance condition the separate coordination of voltage levels leads to an exceedance of planning levels at certain nodes.