The safety

efficiency and cleanliness of energy system are the focus of current research. The traditional energy system analysis

which considers security constraints

is mainly carried out from the perspective of energy flow. As we all know

energy flow is closely related to carbon emission flow

so it is a new attempt to monitor system safety from the carbon emission perspective. Because of the complexity of carbon flow allocation

load allocation or carried carbon emission is the focus of safety monitoring. Considering that the energy system security analysis can not only focus on carbon emissions or energy changes

combining the two studies is necessary. It is necessary to understand the change rule and internal mechanism of the total load-side carbon emission intensity (TLCE) and its limit in the energy system. The focus of this study is on the electric-gas coupled energy system. Firstly

the energy flow and carbon flow models of the electric-gas coupled energy system are established

and the calculation principles of TLCE are clarified. Then

the TLCE and TLCE limits are proposed

and the TLCE limit model and calculation method are established under the system security constraints. Then

to describe the changes of TLCE completely

the TLCE curve model was established. Ultimately

a demonstration through simulation is conducted to substantiate the efficacy of the developed model and approach

and the concept and calculation model of low carbon-based total supply capability and high supply capability-based total load-side carbon emission intensity are proposed in combination with examples.